You got the right idea...but I buy and sell as a hobby and once I get to a newer paid off car I'll start over again with a beater and worok my way up to a newer car again
I did this is as a hobby... And it sucks, and isn't worth the trouble.
You will not be able to sell a 97 P71 for over $1500 unless it is ABSOLUTELY cherry, and even then, $2000 is extremely optimistic. Just being honest, those are the type of cars I bought and sold, You can find 00+ P71's for under 2k in decent shape with under 150K on them (Not super common, but not exactly 'rare' by any means)
Tax/title/transfer is what, $143, so you are already $1150 into the car, If you paint it yourself and have the skill to make it look good, it will cost you $300 at the minimum in paints/detail nick-nacks etc. if you have MAACO do it, it will be $500-600 at the minimum, and this is for a 13 year old police car.
HONESTLY, AND TRUTHFULLY, spend your time and energy into finding a good job, and you will realize it is alot less stressful than trying to deal with flipping cars.
Again, been there, done that. The only time I 'flip' cars now is if I get them IMPOSSIBLY cheap. I'd stick with the crown vic as a DD, and save your money since it should be dead reliable if it was maintained.
I don't mean to 'rain on your parade' but Just be aware as many have said "A car is only worth what someone is willing to pay for it"