Hey Freezy, you can actually build the solar panels yourself, much cheaper, you can buy enough 5" solar cells to make three 62.5w (180w+ total) watt panels for around $100-125, depending on if you want them to include and send you a reverse diode and tin stripping to solder them together, you can get a bz mppt 500 watt charging controller now for around $250 which would handle around 8 home made panels @ 12volts. Wire/cabling costs could vary, depending on how you wire the system, 12/24/48v array as well as how you wire your batteries, 6/12/24/28v, etc..
You can use a 60 or 100 amp breaker box and 15 amp breakers from lowes or home depot to use for a control box for hooking the panels together. Batteries will depend on how much reserve power you desire. Deep cycle are not the best, wont last as long, but work, even golf cart batteries are a better choice. The ones I am testing with deep cycles and are 115 Amp Hours each from wally world.
Most things in travel trailer are already 12v, such as most of the lights, stereo, water pump, furnace blower and most r.v. fridges run of 110v or 12v. Mine has been replaced with full size 110v, but after initial startup, only pulls around 600w while running, Rooftop AC pulls the most at around 2000w, but I have a 8000btu window AC I can pop in at only 850w and works just as well. Mr. Coffee takes 1500w, and I can heat the trailer with one ocillating ceramic heater (900w-1500w). Not always used, but I also have thrown in the cabinets a 1500w toaster oven and 1500w 2 burner hotplate. Two 19" flat screens are 65w each.
Go to any big truck stop and you can find many 12v devices that are decent and will run cheaper on electric than 110v devices, I have a small wet/dry shop vac, slow cooker, hand held vaccuum with beater bar, don't use a hair dryer, but they are available...lol
The biggest users of the electric, just like in your home are going to be heat and ac. As far as the panels and size, by building them, you have more control of the size you want them. I'm not sure how I am going to mount use them yet. I have found a great source for R.V. solar stuff, such as roof mounts that are adjustable, portable stands, etc.
If you are interested in any of the resources I have let me know, would be happy to share them with anyone. Not sure if I can post outside links on here or not.
Many variations to all this, size and wattage of cells you buy, batteries, etc.... Mine is the pour mans version....lol
On a funny side, I spent this past summer running around my house with a 12v battery and a 2000w inverter testing everything in my home to see what I could get away with. My neighbor is intrigued by my experiments and one day I warned him I was going to try to run my full size washing machine off of my get-up. Told him I wasn't sure if one 115ah battery was going to be enough battery, so if he saw my pick-up parked at my back door with jumper cables going into my house, I would be jumping my washing machine!!!!