depends on what kind of condition the car is in. the car may LOOK to be in very nice condition, but if there are any dings, dents, warpage in sheetmetal, or scratches in the sheetmetal they will show when sprayed black. black (although a very common color), is one of the most expensive colors (even on top of pearls and candys since most custom paint shops mix their own which saves the consumer money) to get sprayed due to the amount of body work that usually goes along with it.
a while back before i decided on metallic maroon paint job for my first supra, i was quoted $5500 to get it sprayed black, and thats just with a few minor dings. if you want a professional job, itll cost you... if you pay $1-2000 for a black paint job, itll look like a $1-2000 black paint job (may look good/great, but the amount of body work done, or lack there of, before spray will show). if you go to a shop and get quoted $5000 (not uncommon for black), itll look like a $5000 paint job... if you go to maaco, itll look good until you get it home, then realise you made a big mistake.
one thing you could always do is go to a local college/university and have the automotive department spray it... theyre usually always looking for cars to teach spray techniques on, so you usually end up getting away with paying for the paint itself. also, if you got a good eye, you could strip the paint you have now (not down to bare metal, just get the clear off and scuff up the OEM base coat), and do all the prep and bodywork yourself (including spraying primer and sealer... and im not talking about a rattle can job either), then you may get away with just spraying base and clear and paint costs. remember, the more work you do yourself will always reduce the price you pay to a shop.