I was offered a TEC-9 for sale about two years ago. After a lot of research, I passed on it.
The problem is that the transferable is based off of a crappy gun to begin with. TEC-9s are not known for their high quality, and you will have serious issues with reliability, parts wear, and gunsmithing/service issues. As far as I could find, the TEC9 was not originally designed to be a F/A weapon, so using it as a F/A weapon may unnecessarily stress the gun beyond its already limited capacity.
The biggest problem with owning a TEC-9 is that Intratec, the company that manufactured the gun, went out of business in 2001. It's not like the AR platform, where if Colt went out of business, there would be tons of other companies making AR parts. As far as I could find, the only source of TEC-9 parts would be other existing guns or NOS, which can be found on GB.
So start buying up those TEC-9s on GB, if you buy the transferable and intend to shoot it. The problem with that idea is that semi auto TEC-9s are starting to make a comeback in the collectibility market, so that might be an expensive proposition. Right now, a semi TEC-9 is going for $500 and plateaus around $600.
Also, there are different generations of TEC-9s, with the latter generations allegedly solving the cracked receiver issue. Allegedly.
The offering price was 9k. I wonder if it's the same gun.