Glad to have you here with us in the forum.
Just about any furniture that will fit through your door is okay in an RV. However if you want a sleeper sofa with seat belts, not many residential sofas will fit the bill. There is no single place where you can get the best deals on items. Determine what you need, and do a Google search to find it.
Tony & Ruth........... FMCA#F416727
2016 London Aire 4519, Freightliner chassis, Cummins ISX, 2018 Jeep Wrangler Unlimited, Blue Ox Avail with AF1. TST 507 TPMS