See the whole thing here in Indo is we all live in the "grey area" pretty much all the time - legally, that is.
Now some people can't deal with that at all (Germanics and people from highly regulated societies (Singapore?)) but the rest of us kinda like it and tend to get on with life in spite of it.
Getting on with it, in my case, means to try and understand all the things, bad and good, that might come from the situation.
In this case I view it as a plus, in terms of the charges/rent, that the house has no IMB and has been empty for a while and a minus that the tenancy might be a little precarious. So, what to do?
If you have the cojones for it, take the house as is for the lowest rent you can bargain (for the full tenancy term).
Insist that you only pay a year at a time until the IMB is finished BY THE OWNER.
Don't unpack completely until you have it.