My car is at the end of a 4 year lease. It is a 2004 Cadillac CTS. I would have to finance it at 15,000 to keep it. It has 77,000 miles on it. I can't afford more than 500 a month on a payment. I like luxury cars. Would it make since to...

1. Finance it as is
2. Finance it along with purchasing a warranty with it
3. Pay it off and purchase another car at that price with lower milege.
4. Pay it off and purchase another car higher in price. (I would just have to budget more)
5. None of the above... let me know what you think.

I also need to know where I can find the lowers interest rate of used cars.

Try determining the true purchase price of a car like yours. New Car Prices | Used Car Values - Official Kelley Blue Book Site

The$15K they want from you to keep it is their asking price, you don't have to offer it to them. It is now a used car and you can offer any amount you like.

Knowing that you can't afford certain cars are important also. I like large boats and homes with swimming pools. But I know I can't afford those.

77,000 is not many on a car, I have 260,000 on mine

First unless you were using this for business, leasing it to start with was a bad idea and most likely cost you a fortune in cost.

But if it is a good car, I would buy it, pay it off as soon as possible