We went from a truck and TT to a class C last spring. It has been a great fit for us!
As far as expenses go, a big question is whether or not you use your truck as a daily driver and whether or not you will be keeping it or looking for a replacement daily driver. The other piece is whether or not youโll want to tow a dinghy/toad behind your class C. If you do, the setup on that isnโt cheap, so youโll want to factor that in.
In our case, we were using the truck as a daily driver and traded it in with the TT. We werenโt sure if weโd want to tow a car behind the C or not, so we decided to give it a season and see. In the mean time we didnโt replace the truck and went down to a single car and started carpooling (since whatever weโd buy would need to be the toad if we decided to go that route), then I decided to try public transportation for my commute and fell in love with it (kicking back with my cup of coffee and reading for 30+ minutes each way!) At the same time we found that weโre doing just fine without a toad. We rent from Enterprise if weโre somewhere and want a car, or ride our bikes locally, or even just drive the C to wherever we want to go. So a year later and we havenโt bought a second car and it is working out well for us.
The expenses to consider: insurance, registration, taxes (we pay annual property taxes on our vehicles and RVs here in CT), maintenance of another engine. Obviously weโre coming out ahead in gas since Iโm bussing it, but on trips, the C gets about 1-2 mpg less than the truck and trailerโฆnot really enough to lose sleep over.
We gained living space since our trailer was smaller (24 ft. box), but overall travel length is shorter with our 31 ft. C.
Oh, another thing to consider is what "toys" you bring along in the bed of your truck. Bikes were easy to transition to a hitch mount rack (another hidden expense, a couple hundred $ - we picked ours up used from a friend), but we enjoy kayaking and had to figure out a solution there. We ended up selling off our hard plastic kayaks in favor of inflatables.