The Z32 300ZX, 1990-96 is a PITA to work on. The single worst car I've ever owned to work on. Simple maintenance is a complicated process. Repairs and upgrades are very difficult. Almost ever millimeter of the under hood space is spoken for. Seriously. It is often tricky simply to get a wrench on a bolt, and frequent that the bolt is just the right length to clear the gap.
S13 and S14 240SX, 89-94 and 95-98 respectively, are very very easy to work on. Parts are easily accessed. Parts are cheap to buy. Aftermarket support is strong and usually cheaper than the 300ZX. Upgrades are simple factory bolt ons from other Nissans. Customization options are unlimited.
*Edit* With that said, the 300ZX is a far superior car. However, I would not recommend one for a new driver, especially if he has a heavy foot. The 240SX is very communicative of its limits, and forgiving when you exceed them. It is a car that will teach a driver. The 300ZX feels like your tires are digging into the pavement until it suddenly exceeds it's limits and is very hard to recover. The 300ZX is very likely to be totaled from a front end collision as the floor of the unibody has a tendency to buckle
If you are willing to travel, I recommend using
http://www.Searchtempest.com to find a good deal. When I lived in the southeast I would see sub $2000 running project cars all the time. Be patient and one will come up. The worst thing you could do would be rush to get started on a project instead of waiting 2 months for the right car, only to have it cost more money and take 6 months longer to complete. Shop smart.