Buying used is not a bad thing. RV assembly in general often lacks in quality workmanship. One of the places that can really bite you is water damage from rain, etc. Make sure there is none now and do preventive maintenance soon to ensure there will be none later. That applies to new RVs too. Jayco is high on my list for my next one. I think you're wise to keep the trailer fairly small initially but bear in mind your entire family could be stuck in it for a long time if the weather is bad. I've learned that kids and dogs are able to occupy incredible amounts of space.