I would recommend used for all the reasons listed, plus used units will typically have all the bugs worked out from them.
Do you have a vehicle that could be used as a tow vehicle? If so, your least expensive route would be to go with a travel trailer.
How do you plan on using the RV? Is it to camp in campsites or "off grid" locally, or do you plan on cross country trips with the family crammed into two weeks. (not judging, we do both)
Do you have children? Are you mechanically inclined? What about your carpentry skills? Where will you store it?
What part of StL do you live? We're in the metro-east.
Doug