What model Teco? Saturn S5? Vangaurd V5 or V6? Not necessarily a bad unit. We still service many Teco's. They were made well and were fairly reliable. The only problem now is parts. Not that they aren't available just that they can be pricey seeing as how these units are no longer being produced. Almost any part for some of the later model Teco and MTI units can be had next day.
They can develop problems with the low pressure control systems, but as long as you have a good lift mechanic around you should be ok. As always I recommend having an Inspection done before purchasing, but that's up to you. Just be prepared if a seemingly simple part costs $500.00!
If you get it for the right price and it's in decent condition, it may work out fine for you.