Bought a used coach that came without the sofa. We have the two of us and our son using the motorhome just about every weekend of the summer. We have 72" of width available in the slide for the sofa...
If your slide has a raised floor, don't forget to factor in the height difference when looking at residential furniture. The residential furniture may be too high to sit on comfortably if your feet can not touch the floor.
Many sofa's and recliners have removable backs that make getting them through a motorhome door much easier.