It depends on condition and milage if it's rough and high miles then not much but if you find a mint little 87 with very low miles and was driven by a 90 year man then alot more. Those little four bangers are great if they are maintained and you do the same, my Dad had a 88 2 years ago that was an awesome little truck and he never had to do anything at all to it. Heck you could by an 2000 and up Ranger and have to sink $$$ into it because it wasn't looked after. Just try and find the best deal and if you have any concerns post them on here and I'm sure someone will be able to help you out.
Current 2002 Ford Ranger Edge Stepside, 3ltr Auto.
Other Vehicles I Currently Own
2006 Toyota Corolla 1.8ltr
2000 F350 Super Duty 7.3 Powerstroke
1997 Dodge Caravan 3.3 ltr
1995 Crown Victoria 4.6ltr
1979 Ranchero 500 351w, Auto.
1978 Ford Bronco Ranger XLT 460ci Auto.