I got possession and started work immediately.

You can't always evict for possession if a tenant breaks a lease. 

Usually when you are seeing those Notices and winterization stickers the bank already has taken possession of the property.

POSSESSION: Possession of the property and occupancy (tenants excepted), with all keys and garage door openers, will be delivered to the Buyer when title transfers.

Whatever rights the grantor, the person you're likely buying the property from, possesses at the time the deed is delivered are conveyed to the grantee, you. 

Sheriff arrives and husband and another party are now in possession.  

I like bidding on ones that the bank or HUD have had possession of for 4-6 months.

If it does not, then it has lost all redemption rights and its lien.To get good and insurable title to tax sale real estate, you must usually engage in 3 years of exclusive possession AFTER the tax deed date.  

If you get the property you take possession there but I don't know the details because we didn't buy one. 

And occupied property is worth less due to cost and delays of gaining possession or eviction.Just remember you are competing with people who spend lots of time thinking of ways to outsmart other buyers, reduce costs and competition.