Most adult dogs, even if they have lived outdoors, quickly catch on to housetraining. It is important not to allow them to make unattended mistakes. If you are diligent the first couple of weeks, there shouldn't be any further problems. If you allow uncorrected mistakes to happen, it will take much longer.
Realize that males recently neutered are very likely to want to mark your house. You must watch them closely at all times or confine them to a crate or small safe area.
Hints from various rescue workers:
Before the new dog arrives, spray all surfaces with a product like Repel (TM).
For the first two weeks, when the dog is indoors, keep him confined to a crate, a small "safe" room or leashed to you.
If your situation allows, keep the dog in a confined area with access to an outside area through a dog door. Dogs quickly get the idea of going outside.
If the dog starts to go, squirt her with a squirt gun! It gets her attention, she'll stop and you can take her outside and lavishly praise her.
If you want to allow the dog loose in the house, put a pair of men's briefs on him/her (tail through the fly).
It may take a couple of weeks, but if you are consistent, she will get the idea.
Good Article on housetraining and adult dog: www.VeterinaryPartner.com