What I still don't understand is whether anything has already been done on the house? Earthworks or foundation slab? Basically, it's your problem that you sold the other house. The BU can't be responsible for that. You only sell when it's foreseeable when the house will be finished. Ask the buyer if he would be willing to rent the house to you. Otherwise, involve someone neutral who can organize the whole thing here. We have an additional factor with Corona. Whether changing the BU is worthwhile now? I don't think what hurts you (time) is worth it.