Some tips:
*Make sure you are comfortable in the bathroom & bed, in terms of size. If you are tall or large, that is not a given.
*Actually sit on the furniture (although that is easily replaced.)
*Make sure there is a spot to do your indoor hobbies, whatever they might be. You might need a place for a PC workstation, or just for a laptop. Make sure there is a good TV viewing position.
*If you find a RV with slides that you like, make sure all the space can be accessed without putting any of the slides out. Important for a quick stop. For just one person, I would look for a RV with NO slides.
*Get an inspection!!! From a certified RVIA inspector. As a newbie there are things you just don't know to look for.
*Have an emergency fund for repairs, and an ongoing fund for minor changes/upgrades.