I'll add my voice to those who caution that "investment" and "RV" do not belong in the same sentence.
As for good brands, choose the higher-priced ones - it will be worth it. The constructions and materials will be superior to the lower priced units, which are only intended for "vacation" use, generally considered to be 30 days/year max. "Snowbird" and "fulltimer" qulaity rigs are designed with much heavier usage in mind. Some brands build the quality into their higher priced models while others do it pretty much across the baord.
Fulltimers tend to choose these brands:
Presidential by Holiday Rambler
Travel Supreme
New horizons
Teton
Carriage & Carri-lite by Carriage
Royals International by Carriage
Torrey pine and Kountry Aire by Newmar
Alfa
Alpenlite by Western RV
Other popular brands among those who travel extensively include Cardinal, Jayco Legacy, Montana, Golden Falcon , Arctic Fox & Nash, & Titanium.
Unfortunately, I cannot say that you shoud pick only from this list, nor that every model of the brands on this list are excellent. And there are quality brands that are regional in nature and tend to be unknown at the national level, bu are still fine RVs.
Go to large Rv dealers and Rv shows. Find some brands and models and floor plans that appear to be be suitable for your needs. Then come back here and ask about those specific makes/models and we will try to help guide you.