Foreclusure (trustee) sale is on jan 7. no bidders therefore, title revert back to lender. Notice to vacate in 3 days served. How much longer can the homeower stay in the property? After the trustee sale, homeowner is now a squatter. Is there a squatter (former homeowner) right to stay over and how long?

First stop using that silly term squatter, I don't know that it is even used in real estate any longer. You are the foreclosed owner, But go to the hearing, and ask for more time, if you were a renter living there before the sale, you would have to be given 90 days, so ask for the same right as the prevoius owner.

A squatter entered a property illegally and was staying there without the owner knowing they were their, you are not.

First, this is a question for the lender. They own it, so only they have the power to cut you some slack. Second, squatter's rights vary from state to state.

Massachusetts is one state that has squatters' rights. The Barney-style version is if a squatter lives unnoticed on property for a predetermined period of time, the squatter can actually become the principle owner of the property, via extended residency, if the original owner is unable to provide proof of ownership, can't be found, or is unknown. But in your case, it's clear who owns your property, barely any time would have passed, and I'm certain this lender has done the foreclosure rodeo before so they will know to look for squatters to have them booted. You're better off just asking politely.

Still have a term issue, To my knowledge the term is Adverse Possession , not squatters, any longer
But even if you go to the new or old terms, there are no rights as a squatter, in fact if you were actually a squatter, the owner could merely have the police throw you out at once. So I doubt you want to be a squatter.

Next and I should have asked first time, I just hate that term squatter, it is so misused.

But who was the notice from, was it from a court, or just from the bank ?

If from the bank, they will have to file for an eviction though the courts, before they can do anything.

Now I will leave the legal for a minute, you were foreclosed, that means you have been living there for 4 to 9 months without paying already. So is it not time to move and not causing the bank any more trouble with having to pay for a eviction.