I would not get a free-standing tub. It would actually be a major deterrent to buying the house. Cleaning around/behind and under these tubs is a chore. Looks like you have an oversized tub. I'd shop around for a white tub that will fit your opening as it exists. Let the buyer change the tub if they don't like it. You should concentrate on updating to current, not getting the trendiest expensive things since you're wanting to sell. Good luck!

Any chance of doing an undermount tub? It looks much sleeker than the drop in and is probably easier to live with than a freestanding tub. Many of the freestanding tubs I've seen just don't look comfortable to use or practical to get in and out of. If you have the tub deck, you can sit on the deck and swing your legs into the tub rather than climb in.