I don't know about your particular install, but you need more information. First off with a single house battery you are not going to be running much with an inverter, meaning it may be great for plugging in your cell phone charger, maybe a modern flat panel tv that draws 30-40 watts or a notebook computer that draws the same. Think of your house battery as a fuel tank, the smaller / fewer you have the quicker you are going to run out of fuel. Also you need to know the size of the included inverter as well as what you plan to run, there is a big difference in a 200 watt inverter and a 2,000 watt inverter. You also need to learn the difference between a modified sine wave inverter and a pure sine way model, as well if you plan to run anything that needs pure sine wave. Lots of stuff don't care (things like computers and TV's with switch mode power supplyes), on the other hand microwaves are one where it can make a difference as they tend to overheat and burn out when connected to modified sinewave inverter, the question then becomes one of is it worth paying an extra $250 for a pure sine wave inverter to extend the life of a $80 microwave oven (if you have a fancy $500 microwave/convection oven the answer gets easier). A 200 watt inverter is enough to run many modern low powered items like the phone charger or flat tv mentioned above, what it will not do is let you run your microwave oven that may draw 1,500 watts. Think of the inverter as the size of your engine, the bigger it is the more load it can pull, but also the more fuel it consumes, in the case of a modern inverter, the only downside to buying one that is too big is inital cost, a 2000 watt inverter powering a 40 watt TV will consume about the same power than a 200 watt inverter under the same load.
Back to that initial sizing, if you have a 1,500 -2,000 watt inverter and a single battery you can use it to power higher electrical draw items, if you run it for a short time, meaning you can use it to warm instant oatmeal in the microwave, but not to cook a turkey.
As to the solar ready / solar prep on many RV's this just means they have ran (an oftern undersized) wire from the roof to the battery bank area for you, if you are lucky they will have put quick connects on the ends of the wires. You will still need solar panels, mounting brackets, and a charge controller. Now as to sizing roof top solar as a general rule of thumb you want less than about 250 watts of solar panels per deep cycle battery on the upper end, and at least 80 watts of panels per battery on the lower end. There are many cheaper off brand imported panels on the market priced in the $1 per watt ballpark, some are better than others, they often do not perform as well as the big name panels, meaning a 120 watt fly by night no name import may perform as well as a 100 watt big name panel when used to charge a battery. (I am not claiming false advertising on watts here, just lack of optimizing the exact output for charging purposes) Many of these cheaper panels are not built as well either, with thinner and weaker metal frames, which may be an issue with wind loads at highway speeds.
Let me compare 3 Solar panels I own, that I have bought over the last 10 years or so for various small stand alone remote solar applications. Just focusing on the metal frame that holds it the panel together. The big name panel uses a fairly thick E channel aluminum extruded frame which is anodized for extended outdoor life, import panel a (Newpowa brand bought last year) uses common U channel all the way around and is about half as thick as the brand name panel, import panel b (no name eco something that was $10 less than the Newpowa also bought last year) uses U channel on the sides only and L channel on the ends allowing for much more flex.