My wife also had bad allergy/asthma problems which is why we had to move back to the mainland from Hawaii :(. Oh that hurt.
Can't offer much help other than what has already been said but owning a previous lite Fiver I would not recommend for full time or half-time. The occasional weekend warrior adventures and a couple week trip in the summer worked fine but beyond that no way. What I have now I consider a full-time RV unit but that is just me and I'm a long ways from retirement. I'm sure your needs are far different from mine.
Mobile Suites, Carriage (redwoodrvfamily.com), Alpenlite, NuWa, Lifestyle, Heartland, Landmark are the one's that ranked high on my list for full-time.
In my experience (somewhat limited compared to some of you here) Going the cheap route has it's pro's & cons just like anything new these days. We live in a throw-away society and nothing is built to last very long these days. Warranties are more critical but they sure as heck don't cover everything. Just got to be willing to accept and plan for the inevitable consequences regardless of which path you venture down. Chance favors the prepared mind.