Starting 92 chevrolet lumina after setting 4 years, what to do???

I'm buying this car. It has been setting for 4 years. It had about a 1/4 tank of gas. I filled it up with top-grade gas & added fuel additive to help evaporate any water. I tried to jump start it & it seemed to want to start, but wouldn't. I haven't paid for it yet, but would appreciate any suggestions on what I need to do to get car started. I also was thinking of having a mobile machanic stop by to help? It has 86K miles with a 3.1L fuel injected, V6, one owner who drove it & took care of it well. Again, your help will be appreciated for sure.