"Live aboard" has different connotations to each of us. We have lived on our boat while cruising for up to 5 months at a time. Moving every day or two, sight-seeing, dividing the time between marinas and on the hook; using the boat as a camper while on land. Last year, while working summer jobs in Friday Harbor, we lived on the boat for 4 months, and did additional cruising before and after that time, total of 6 months onboard. We have a 25 C-Dory, similar in floorplan layout to the R-25, different in execution. Realistically, the 25 is the smallest boat we could have done this on, and many folks thought we were insane to do that. 😉
We all have different "minimums" for comfort. For us it is: electricity, heat, cooling, fresh water, hot and cold running water, means to cook (microwave, cooktop, grill), entertainment/information (satellite TV, satellite radio), storage space for clothing and food/cooking gear, a comfortable bed, comfortable places to sit. A full camperback enclosure gives us a nice "sun room." We do shower on our boat each day (both of us prefer that over schlepping our stuff to a marina shower).
There would not be the space nor facilities for all that on an R-21. Don't get me wrong: I think the R-21/R-21EC might be one of the cutest boats on the water. It would be good for an occasional weekend out, as long as you are good with boat camping (as opposed to living onboard). One person who was a minimalist might be able to extend that time a bit longer.
My wife and I worked together for over 30 years. Motorcycle camped across the country. RVed for months at a time when we moved up from tent camping. Traveled by various sailboats before we retired. I share this only for reference sake... it is important to know how you intend to use a boat and what you really need for personal comfort.
The cabin on the R-21 is small; the cockpit is large, with an engine box taking most of the middle of that cockpit space. You can enclose the cockpit with a camperback enclosure, which will give you more living space (similar to a tent). Each person has to decide if it is "enough." Consider "elbow room" if there are two of you.
In addition to the living accommodations, we really appreciate having a good chartplotter, depth finder, radar, VHF, and autopilot. An electric windlass makes anchoring easier. Good binoculars and a spotlight. A couple small inverters to use for charging devices (computer, iPad, phones) while underway. A generator is nice when at anchor.
You can certainly live more minimalist without many of the above. Depending on one's personal comfort level... at some point, it can become endurance rather than adventure.
Good luck with your decisions.
Jim B.