1) Find out how much a RV park is going to cost you. In your area, they may be as much as rent.
2) Add propane to your list of monthly expenses.
3) Find out if the park has metered electric, in which case you will get a separate electric bill. That will be substantial in the summer when you need AC.
4) You will need a good place for a cat pan. Those are hard to come by in a RV. Any odors will be worse in a small space. You will have to buy cat food, vet bills, litter. Remember this is a 15 yr + commitment. If you can't afford to take care of an old sick cat, don't get a young healthy one. And even young healthy cats can develop issues requiring meds, surgery, vet visits. Don't get one if you are gone all the time.
5) If you want to travel in it, get a tow vehicle you can afford and then buy the trailer. If you want to stay put, get someone to move it for you and don't worry about it.
6) You will be fine with the standard water heater. You can always upgrade later if you want to---IF a 10 gallon will fit in the space.
7) You mentiononed your wife. How does she feel about this? Happy wife, happy life. Make sure she has a space that suits her.
8) Get the insulation package.
9) Get up on the roof about twice a year and inspect every single seam and roof penetration. Caulk if needed, or cover with a sealer tape called Eternabond.
10) Check for condensation in exterior lights. That means that water is getting in. Caulk well around them, make sure the weep holes are on the bottom, and make sure the weep holes are open.
11) Make sure the weep holes are open in the windows.