I am about to buy a 1984 Mazda RX-7 GSL with about 45,000 miles that has sat outside for 6 years. Apparently needs crank shaft seals & won't create vacuum. Is this costly or major? Could we do it?

As long as you're willing to replace the engine, which IMO is a VERY realistic scenario for a rotary engine that's been siting for THAT long....and yes, it will cost some $$$ to get her up and running after not being properly cared for.

Try this first: While cranking the engine, slowly pour trans fluid down the intake. By providing lubrication, it's possible to build up your vacuum and get it started. It works with flooded rotary engines too! The seal get dried out and won't seal. This isn't fix - it's a cheat. A new motor for the car isn't that expensive when you consider how stinking easy it is to change out. Besides, with that few of miles on it, a new motor will top off a nearly new car. PS: if you do pull the motor - change out the clutch components just for CYA.