Not easy questions. Series I's are a niche market and if truly original often are hard to find parts for. IIA's are the best (in my opinion) due to the good parts availability and relative ease of working on them. Some people prefer 88's for the smaller size and for slightly more maneuverability. I prefer the 109's because the ride is a little better and they can haul more.
You can buy and resell, but you're likely going to lose money on this deal. Just know that going in. Lately the market has been overrun with "fortune hunters" thinking all these old Rovers are worth a fortune and they just aren't (unless particularly rare examples or original condition, or have undergone a proper restoration). Beware the ones with good looking paint and nothing else. They abound. Do some searches on what to look for in a good Rover and then set your price limits on that and start looking.
Good hunting
61 II 109" Pickup (Restomod, 350 small block, TR4050)
66 IIA 88" Station Wagon (sold)
66 IIA 109" Pickup (Restomod, 5MGE, R380)
67 IIA 109" NADA Wagon (sold)
88, 2.5TD 110 RHD non-hicap pickup
-I used to know everything there was to know about Land Rovers; then I joined the RN Bulletin Board.