You can do a search on this forum about tips on buying a TR7 or check buying advice on home page. If it's running well as you say the thing to be concerned about is how has it faired with rust. While wheel well rust on the lip is pretty easy to see check closely under the sills (beneath the doors) and where the rear lower suspension links attach to the body as these areas are more difficult and expensive to fix. If these pass, the her price is a good one. I'd grag it.
I see you're from Ione. My Spider spent it's life around Stockton, not that far away. It was totally rust free except for the odd bolt and nut and the odd spot of surface rust on the edge here and there.
The car is over 30 years old and depending on the maintenance it's received over the years it may need some attention as you drive it. Change fluids and clean all electrical connections and seal with dielectric grease. As with any 30 year old car it requires periodic maintenance not like current cars which are relatively maintenance free. As such it's more of an enthusiasts car meant for those who don't mind rolling up their sleeves and doing it themselves. Don't get me wrong, it's a reliable car if looked after. Lot's of help on line and books available, relatively cheap parts, most parts are available.
(By the way, I had a '69 and a '70 Beetle in the 70's I used as a work vehicle that I was going to turn into an Aztec 7 but never got to it.) I obviously got my wedge fix from the TR7 which I also wanted in the 70's.
TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra