If you or your wife have arthritis or other problems climbing over each other and climbing down a ladder, in the dark, in bare feet, to go to the bathroom, you'll need at least a 27 foot long Class C with a rear bedroom that has an "RV Queen" size bed. A few rigs are designed with a small slide that provides access on both sides of the bed and at the foot. This makes possible getting out of bed and back into bed without waking your partner. Four grand kids can sleep on a convertible dinette bed or jackknife sofa and in the overhead bed. A Ford E-450 V-10 gas engine is quite standard. Most class C's use the same appliances, furnaces water heaters, air conditioners, awnings, generators and plumbing. Our appliances started to need replacement at about 10 years, so I advise beginners to buy 3-5 year old rigs if they can afford them. Make sure that you and wife really want to take on the RV hobby including costs of ownership, and effort of packing, driving, setup and stowing and unpacking after trips. It's a good idea to have a professional truck mechanic and RV expert inspect and test a potential "buy" and get a written estimate of what it needs in repairs or upgrades before you sign the papers. Get all promises by dealers in writing on the sales contract before you sign.