Hmm....so are you certain that if you (and siblings?) buy the house from them, that they will indeed maintain the house? What happens when the property tax bill comes due, or a new roof is needed, and they answer "Well, you have the money, are you going to force your mom/dad to pay for this when you have more than us? It's your house, you take care of it. We don't care if we pay the taxes, our name isn't on the title!"
Are you willing to kick them out of the house [-]if[/-] when they ask you to pay for something more than you already have? Are they going to pay you back for the car? When? what payment terms?
If they goaded you into buying them a new car, why would real estate taxes be any different?
Perhaps "goaded" is a strong word....but how could two adults,
both working in their 70s, need their child to buy them a car, especially after declaring bankruptcy 7 years ago and (assumedly) wiping their debts out? Are they already up to their eyeballs in debt again that they can't afford to buy their own car?? I only see issues coming up with these parents as your tenants. Likely sooner than later.