It all depends what kind of traveling you are going to do and where. Also, the size and age of the unit you are going to purchase.
Personal example: I bought our 24' E450 C to use as a tow vehicle and home base at the track to support the family auto racing hobby. Definitely a better than breakeven deal most weekends, as where we go is for a couple of nights no more than 250 miles away. RV towing the trailer at 6 or 7 miles per gallon is a fuel expense of maybe $225, vs. towing with the truck and staying in a hotel, which while the fuel is 3/4 the cost, there is easily another $200 in lodging plus food on top of that. The RV really comes out ahead if we are somewhere for a week. An example is the week in March we spend in Sebring, Florida, where any hotel room you would want to stay in is at least $250/night with a 7 or 8 night minimum. We spent about $850 on fuel for the 2200 miles down and back, $100 for the camping pass at the track, and Wal-Marted the overnights each way. Food was what we would have eaten at home. Even if we had driven a 30mpg car there, and used a cheap allowance of $75 per day for eats, due to outrageous hotel rates the trip would have been almost $3,000 instead of the $1,300 it was.
I bought a new RV, negotiating a good deal, with the intent that I was going to keep it for 10+ years. While there are usually a few fix its required on a new one, and early depreciation can be a hit, if the unit is owned long term, the benefits of getting all the life-cycle out of the expensive components IMHO makes it a better deal that buying something older and dealing with 4-figure repairs on regular intervals for things like generators, refrigerators and a/c units.