How bad would the repossession by 'we finance auto' affect my credit

Since you bought the car from a ''buy here pay here'' place, your credit was not good to begin with, and if this one gets repoed that will totally destroy your chance to buy another car. Most of those places give you a chance to rebuild some credit, and the repo will show lenders you're a very bad risk.one few if lenders would take.
I know it stinks, but keep the car if at all possible, and try for a conventional loan when this one is paid off.

if they did reposses the car, how would u get another? if they did repo the care they would sell it & use proceeds to pay on the loan balance. then whatever loan balance is left over u will still be responsible for. it takes a very long time to get this off ur record, i'd say maybe 5 - 7 yrs. but with the passing of time & a better, income, etc. u will find companies willing to give u another chance for a loan. but people who have the worst credit will always pay the highest interest rates. so keep this in mind too.

If they report a repo, & with no positive credit & only a repo ur credit report, of course ur credit rating would be terrible. Go to FTC.gov & pull a free copy of ur report. You can see if they r currently reporting the loan. If so u can be assured the repo would show up, if not they then that means they may not report payment history, but they could report a default or judgement. The same way a cell phone company or utility would do.
Try to negotiate a settlement to pay off the loan, maybe they give u an X% discount for a lump sum payment. Get EVERYTHING in writing. And even then who knows what could happen. Actually I would only pay them through an attorney or CPA, ie they give the attorney the title & u pay the attorney, who signs over the title to u & pays the dealer.

Be careful, simply asking for a settlement can be considered a default, so they could repo the car.
If u default they repo the car will ''auction'' it for some fraction of the value & then try to collect the deficency balance from you, with interest & fees. Trust me they r the experts in this game, they know exactly what they r doing & have seen any & everything u could think of.

7 years is normal for 'black marks' on your credit for evictions, repossessions, etc.
Businesses like that prey on people with low finances, etc. They're vampires.but they did not force you to buy from them, so you must recognize your responsibility.

If you are under 21, you might be 'off the hook' because, legally, the contract with them is not valid: you're a minor.

IF your finances improve, try to work something out with them.

This would have a huge negative impact on ur credit. If u want to get out of the loan & forfeit the car, u can arrange a voluntary surrender where u basically go through the reposession without having to actually go into default. You will still have to make some sort of financial settlement but if u go into default, they will take the car & still come after u for the unpaid portion of the loan. So it is cheaper for u to do a voluntary surrender. That will still have a negative impact on ur credit but nowhere near as major as a repossission.

It would depend if the dealer reported you to credit reporting agencies. If you do not want to continue with the deal, contact the dealer and offer to bring the car and the keys back without badmouthing him. Maybe he will call it square if you are cooperative.