Having only rented a crummy Class C several years ago, we umped in with both feet as you contemplate. We sold the house, bought the 33' used rv mentioned in previous post, and have been happily fulltiming for 10 months. We had a 4 bedrooms house, and adjusted to smaller space just fine. As a newbie, I did not want to sink a ton of $ into my first rig; we had lots to learn. Some say buy "the one" once, but I would not have known it was "the one" . As a newbie, we decided to buy a solid, budget friendly one and trade up later if needed. Of course I have not been through the selling experience yet, but remember in one year an expensive new rig probably would have depreciated by more than my user MH cost. Some say buy bigger than you think you need. For our first one, we bought as almost as small as we thought would do, knowing we could move up. So far neither of us feel compelled to buy bigger. There is more than one way to handle it; you will have to decide what is right for you.
So far we have not run out of storage or carrying capacity (two people, no pets). Are you planning to tow? If so factor that into your capacity and budget. we are not towing as of now. I drive and spouse follows in chase car. As a newbie, the having a friendly car behind is rather nice, and we generally do short drives then stay awhile. For us, getting set to tow would be pretty expensive as needed a different car and all the equipment, and it might put us choose to our rear axle capacity. Though we could afford it, for now we are happy enough with our current arrangement. If you wish to tow, it will probably influence you buying decision. If you are lucky, you may find a private sale with toad included or at least tow bar.