Good does not adequately describe a solar system in a RV. Excellent, or best thing I did, or saves the batteries, and gives 9 years life out of the batteries! That is more like it.
You can buy a solar panel from this place, SunElec.com
for about $2 per rated watt.
Some have installed a 400 watt solar system, and then no need to worry about battery going dead, watch TV via a inverter, or run a video game, ect. Yet 200 - 300 watts is normally plenty for a average RV.
Your budget should be about $400 for a 200 watt solar panel, and $125 for a controller, $25 if you make the brackets yourself, and shipping will be added to the solar panel. Wiring will be about 25 feet of #10 UV rated direct burial wire, you can buy a 25' roll of it at Home Depot, it is gray outside covering. You can run the wires from the roof via the refrigerator vent to a suitable location for the controller in the basement in my case (was in the closet next to the refrigerator at one time) then to the battery.