I recently bought a '75 GMC. At the previous owners house, she fired right up. I get her home and nothing! The couple of times I did get her to fire up, had to jump the battery but the guy said the battery was new... any suggestions?

 

Are the terminals clean and tight? Check that first.
If you believe the guy, you may have something in the truck that is leeching power from the battery.
A "75 doesn't have the complicated electrical system that are in later model vehicles.
If the battery is good, you might want to pull fuses out until you find what circuit is killing the battery.
If the battery has under 13 volts, Get the battery tested with a load tester..
If it is good and there is no leaching, you may have a bad starter or solenoid.
Hope this helps.