My only sortie into the world of multihulls was when I bought a Piver 35' Tri as a fixer-upper. The deck was like a tennis court, down below was cramped, the thing flew on a reach, was downright dangerous when running before a sea, and was almost impossible to tack from close hauled. (Frequently, when no one was looking, I would do it ***-backwards and change direction by gybing
The fellow who bought it from me 9 years ago is still sailing it along the east coast of Australia and absolutely loves it....But it was, to say the least, not my cup of tea.
However, repairs to a glass-over-ply hull are easy to make, the plywood-glass hull is strong, they have a shallow draught, they have positive buoyancy and will remain afloat no matter what happens, and despite the frequent feeling that they want to capsize, they are very stable and, as most cruising tri's have a short mast, they will generally remain upright.
Tri's will heel a lot on a beam reach.
The major problems with trimarans concern older boats made in backyards. Tri's are stable and reliable when properly made; but many older boats may have been built with inferior grades of ply, non laminated crossbeams and, may have been extended without the appropriate design and engineering modifications.
Problems rarely surface in protected waters, but in the open ocean, many of the older Brown and Piver designed boats had catastrophic failures. This was not the fault of these excellent designers, but of the hippies who slapped them together before embarking on their quest for Nirvana.
A good surveyor will sort out the good from the not so good. You can buy a heck of a lot of boat for very little money.
Hope this is of some help