Yes... bid appropriately.
They don't always know if they are occupied or not. Sometimes it is hard to tell.
Could be the past owners, could be renters.
You would have to evict, if there is someone in the property.
If it was the past owner, probably not hard to do.
If it is a tenant, there could be a lease in place.
Often their prices are too good to be true. If you are thinking about the one on Tioga, that could be the case. If I remember correctly one of my clients bid over the asking price, but they rejected the offer.
Often you cannot get inside to see the home. So no inspection, no observations, etc. So difficult to know the condition. You might get a great deal, then again you might get one that is missing everything. You just never know.