HI,
I lived full time in my RV for about 6 years. I have a 400 watt solar system that was installed between 1994 and 2000. I did not start full timing until 2006.
4 golf cart 6 volt batteries are plenty for any normal user. You really do not need to carry more batteries, just more solar panels if you find that you are running out of power daily.
You can buy a 140 watt solar panel from this place - 12 volt nominal, with a frame to mount to the roof, and only around $229 a few weeks ago.
SunElec.com Some of the solar panels sold at Harbor Frieght, or some 'hyped up late night TV show' will be folding or perhaps walk on flexible cells. These are normally sold for close to $4 or $7 per rated watt, while the panels above is well under $2 per rated watt. Also the flexible cells take a lot more space to mount on the roof. Some have suggested gluing on the panels, however this will limit the heat lost - compared to a solar panel with 1" of air under it, and also it will shade the RV roof, keeping it cooler inside.
For mounts, I used 6" long aluminum 2" angle, about 1/4" thick (home Depot) and UV rated #10 wire from home Depot. You can run the wiring down the refrigerator vent of most RV'ss.
The 'solar option' that I have seen on my RV's seem to be based on 1997 prices for solar panels, in other words retail close to $4 per rated watt! Installed, I have seen a 100 watt solar option cost $855 or more!
100 watts is not enough. It will slow the discharge of the battery, but will not charge it well. Your RV will consumer 35 AH daily just to run the CO detector, propane leak detector, and the refrigerator. Each of my 120 watt panels can put out aboout 35 AH daily recharge, this stops the dishcarge, and can fully charge the battery on a long day, or bright sunshine found above 5,500' altitude.
Cooler air and higher altitude both will produce more power per hour, even more than the panel is rated at!
Good luck,
Fred.