I can give you an idea of our costs for a small travel trailer (16' model). Up front costs were 13.Xk purchase price, perhaps another $800 of stuff done to the car (tranny and steering fluid coolers, hitch), and a few hundred bucks of random gear we needed/wanted on board. So call it $15k in for a new small trailer ready to go. I assume that at the end of 10 years I will be between sellinshing it off a cliff in the middle of the night.
We us it 25 to 30 nights a year plus it sits in the driveway for use as occasional guest quarters. I am not mechanically inclined, so the dealer does most everything. Maintenance costs are $200 for winterizing/dewinterizing, $100 every 2 years to have a leak test done,
for recaulking as needed (haven't needed it yet), $150 for the RV insurance policy, and maybe $30 of propane. We are in our third season, so aside from some light bulbs thing have not started to wear out yet. I expect that after 5 years we will need a set of tires ($500), and prob start having a few things wear out/break (
but figuring 300 to 500 a year after the 5th year). So if you annualize the tires and toss in something for repairs, we are probably looking at 700 to 800 a year to keep the thing running. Maybe toss in $1500/year in depreciation on the trailer.
Operating costs will vary. I generally expect to spend something like $25 a night on campground fees (varies considerably from zero for boondocking to $100+ in the most ridiculously over the top resorts) at state and county parks. We also see our gas mileage drop from about 25MPG to about 12MPG, so add in something extra for gas, which depends heavily on how far you are going and how often you move.
We are taking an 8 day summer vacation next month to a spot about 250 miles away. The campground will run around $200 and the gas will probably clip us another $120. That is pretty reasonable overhead for 4 people for 8 days. There is a small offset in theform of reduced utilities costs, as I won't be home running the ACs flat out or using my own water, etc.
My understanding is that motorhomes are considerably more expensive to buy, maintain and run, which is a major reason we chose a small trailer. If I wanted to do this on the cheap, I would look for a 2 to 4 year old trailer that you could hopefully tow with your existing car.
Personally, I think that the trailer is a very economical way to travel and would be even more reasonable if we had more time to travel with it.