When you say 1/2 the car you also need to put a cap on the car. Is she getting a Tesla or a Hyundai? 

I think it's wisest to get a reliable, cheap car for a first time car. The money they are planning to spend could purchase a brand new, small car. Imagine how upset you'll be if she wrecks it. Is she responsible? Does she take good care of things? I would honestly cap the funds at $3-5,000 for 1/2 of a decent used car.

Totally agree with this. It doesn't even matter if she does or doesn't take good care of things, as a new, young driver, there is a good chance of some kind of wreck within the first year. And, insurance will be less on a cheaper car.

I'd say paying for the car itself is a lot more than most of us had when it came to our first car. Is it just me who thinks that if a teenager or young adult can't afford to pay to keep their car running then they shouldn't have a car? It's a good lesson in life too. Don't buy what you can't afford. I had to save up to BUY my own car, and before I did that I had to do so much research in maintenance cost vs purchase price and mileage because it was my own money. My SD on the other hand kicked up such a stink over her FREE car when DH refused to pay for her car maintenance and petrol after she turned 21 and was employed full time!

Just from my perspective: Husband is a car mechanic, and people sometimes just give him free cars. He will go to local junkyards and fix them up and either keep them or sell them. Sometimes he pays a little (say trade-in value) and then he will drive it for a while. Then sell it after fixing some things.

And sometimes he finds things on facebook marketplace that are too good to pass up.

That being said, he will probably find a really great deal on a higher-end car, used. Fix it up. Or have SD15 drive the beat up old wagon for a while and then do that.  When she is permitted of course.

He will more than likely not spend more than $3,000 on this.

As to paying for gas and insurance, she will need to pay for that. He will do maintenance, probably for free, because he can.

I think that the issue of Toxic Troll paying is a non-issue: she is not currently working and I doubt that she will contribute a single dime to SD15 driving/car.

Neither will I, because not my kid.

As to mentioning the child support - wow! He must be doing very well, so thats very nice, and I am in the camp of "inform the kids". I think that children, while you should be mindful, really should know that their father is contributing every month to their mothers household for their support. They dont need to stress the household financials for a while, let kids be kids, but I think its necessary when the BM tries to make the father out to be a deadbeat who doesnt support his children.

I am very supportive of SD15 driving and getting a car as soon as is healthy. Watching and seeing what happened with Feral Forger SD22, who doesnt drive, no license and no car ever, and currently not working and no college. Shes so used to people driving her everywhere. All the time. No real ambition either. Just nothing. So I am more inclined to help pave the way for SD15's further independance.

Good luck!

My thoughts:

1. I definately think that all children with separated parents should know that one parent contributes to the other household to help support the child - I don't think there is a minimum age where this is inappropriate. And when they know the value of money, I do think it is appropriate that they know the order of magnitute of that payment if one parent claims that they do not recieve enough etc. 

2. This is what I would do if I were your husband. I would tell your SD that he is willing to contribute towards getting her a car and he will match the amount that BM contributes. Then SD can talk to her mother and find out how much (if any) she will contriubte towards buying a car. This way your husband is not dictating to BM how much she should be paying towards a car which I do think is rude to expect BM to match the 7-15k price that your husband came up with without consulting her. If BM refuses to contribute or only contributes a minimal amount then your husband could choose to fund the car fully himself if he wants or insist that SD contriubte in some way that is appropriate for money that she can reasonably earn.

3. If your husband wants to also cover lessons and/or insurance (I would not cover gas if I were him - SD should at least finance this) then he could take that money out of the extra $400 a month he gives BM beyond the required CS amount. If he were to do that I would give BM a month or two's notice so that she can adjust her finances accordingly. 

I bought BS23 his first car - paid 10k for it, it's a great used car that he will be able to drive till the wheels fall off. Until he's 25, the car is in my name. he pays insurance, gas, maintenance, registration fee's etc...

I gave SS28 my old truck. It was fully paid for. He registered it in his name, paid the insurance for a few months, stopped paying the insurance, registration was suspended, was driving around with no registration and no insurance, cops stopped him, arrested him, took the car, he never bothered to retrieve it. Now he has nothing. 

I did my part, he shat all over it, now he takes mass transit everywhere. 

Your DH should offer to match whatever SD manages to put together for a car, with or without BM's help. If BM drops 2k and SD saves another 2k, he should match 4k for the car. make sure it is NOT in his name, let BM worry about that headache.

I have two SD's.. the first one we bought her a modest used car.. but she was supposed to cover gas and insurance..then when she graduated HS.. we helped her upgrade to a nicer used car... and actually she was supposed to repay us a couple thousand we spotted her for that.. and later we found that her grandparents were often giving her the $ to pay her insurance.. she is the spoiled and entitled kid by the way.

YSD.. we told her she had to save up half of the car plus a few months insurance in advance.. she did.. we found her a reasonably priced vehicle that she did pay her half (though her grandfather got mad because we insisted she pay us the half)..and she paid all her expenses on that car... a few years later when she got her first job... she got a used car loan on a 5K vehicle and then a few years later did buy herself and finance herself a new car off the lot.. and still pays all her bills.

I think that kids appreciate it more when they have to work to earn what they have and keep it.  I would be liable to insist the girl also come up with some of the car cost... and prove savings to cover the other costs.. AND.. if she lives with mom primary.. it will be mom's insurance that should cover the car.

We paid for everything so I cant address your "who pays what" question.  But with 5 kids all teenagers, my DH finally realized that the more tank-like the car, the better.  Every single one of our kids had an accident in the first year, never serious thankfully and NEVER their fault, of course.  But the heavier the car, preferably a used car, the better.  They all each had a ticket the first year, too, again NEVER their fault.

Used, heavy car -that's the ideal.

I'm going to say that I don't agree with parents buying their kids cars.

I think kids should get a job, save up and buy their own cars. That's what we had to do, and that's what my sons have done.

However, that is my personal opinion.

I just don't think kids learn life's lessons if Mummy and Daddy pay for everything, always bail them out etc...

Ex bought his daughter a car, paid all the maintenance and expenses.

She crashed it and wrote it off. They got some money back from insurance, which he topped up to buy Princess another car. 

The accident was her fault, but she won't own that fact.

Ummmm why are these parents buying their 16 year old kid a car?

Is it because she needs it for work TO help support the family? Or because she has activities you THINK she is mature enough to drive herself to?

Kids need to get a part time job, save money for a car. THEN also pay for their own insurance.

Have you priced the cost of insurance for a 16 year old?

I believe someone above said the kid needs teeth in the game..YES I also agree.

Ummmm why are these parents buying their 16 year old kid a car?

Is it because she needs it for work TO help support the family? Or because she has activities you THINK she is mature enough to drive herself to?

Kids need to get a part time job, save money for a car. THEN also pay for their own insurance.

Have you priced the cost of insurance for a 16 year old?

I believe someone above said the kid needs teeth in the game..YES I also agree.

In million dollar homes would have their parents by them an old used car and the kids had to get a casual/part time job to pay for insurance, gas etc. They had that car until they saved the money to buy a brand new one

My exH has never and will never contribute a dime more than what is ordered in CS. It's not much but I have always put that towards DS expenses and try to out some away towards college.

That being said DS and I have an agreement that he needs to put money away towards a car. Whatever he manages to save I will match it towards a vehicle when he is 16. At 13 he has already managed to save $1100. 

As parents we want to help our kids but also teach them responsibility. I believe a kids take better care of and appreciate things more when they have to work for then themselves.