In addition to the above suggestions:
If you are taking short weekend trips, you probably won't carry 1500 lbs, and you probably won't mind pushing the limits of your tow vehicle. If you are travelling cross-country, you will carry a lot more, and you will want more power.
As to your question about depreciation, try this. Go to nada.com, put in a model number that you have looked at, and see what the going price is for a new model. Then check the market price for a one-year old model, then a two-year old model. You will get a feel for how quickly they depreciate.
There are plenty of nice used RV's available.