Rather than try to guess what you might get into, I will share my experience with my Jalpa and you can get an idea of what it is like to work with one of these cars.

I paid 33K for a Jalpa. Thought it was in good shape and needed only a few minor things. Here is what it needed and what it cost.

Ignition switch was bad. Not available. rebuild 500
Brake booster not working due to old fluid. rebuild 500
Labor for removing and installing above. 500
Ignition wires need to be replaced. 250
Time spent at shop making the old ignition stuff function. 500
Found a broken mount point for the alternator. Weld 125
Fabricate new alternator tension arm. 200
Carberators were a mess. rebuild 1620
Re-key the ignition. 300
purchase hoses for smog re-connect. 30
New weather stripping for big leaks. 600
Stainless braided lines to prevent fires. 300

Next steps
Tune up ?
Install weather stripping ?
New paint ?
stainless steel oil lines ?
MSD with rev limiter 300
New belly tunnel cover 800
Fix door locks ?

I bought this car 8 months ago and have not driven it more than back and forth to the shop and that stopped 5 months ago. Most of my issues are not that serious or expensive indidually, but things add up fast. I will probably find more when I start driving it. Take people seriously when they say it will be expensive to fix up. Do-able and noble, but be prepared.