Welcome to group. There's allot of information here just ask.
As for your question, yes Sunlines are built well but as with any trailer they are prone to leaks. My advice is to get a pinless moisture meter. Great tool when looking for a travel trailer. Take meter inside and check around for moisture where ceilings meet walls and where walls meet floor. Damage may not show inside or out but can be rotting wall joists floor or ceiling. Walk away unless you are willing to do extensive repair work.
Good luck Jim
Jim and DW
2001 T-2553 Sunline Solaris
2006 GMC Sierra Duramax 2500HD 4X4
Firestone Transforce AT tires
Reese Dual Cam Sway Control