You question is a little long and to some extent unclear. Speak with a competent attorney in your area.
NORMALLY DOES EACH PERSON PRESENT GET CHARGED WITH POSSESSION
No. Officer's discretion. If anything would be normal I would say it would be to charge the homeowner/renter with possession and others with promotion among other charges. However, officer's discretion.
CAN THE EVIDENCE GAINED IN THE SEARCH DESCRIBED BE USED IN TRIAL
Maybe. Actually, it is very likely the evidence (plain view, probable cause, whatever else the DA claims) would be allowed based on the facts as given. Maybe on appeal a different result could be reached.
WHAT SHOULD HAPPEN
The person charged needs a competent attorney, asap. Everyone else should probably also speak with an attorney just in case. Every step of the way the Defendant should be vigorously defended and the State should be forced to prove its case, unless of course a decent deal can be brokered (one usually leads to the other).
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There are exceptions to the requirement that law enforcement officers obtain a warrant prior to searching a person's house. However, based on your question it is unclear whether any of these exceptions applies. If an exception does apply, then the evidence discovered inside the house may be admissible at trial. If no exception applies, the trial judge may suppress (exclude) the evidence at trial. You should speak with an experienced defense attorney in the area asap! That attorney will be able to advise you further regarding the merits of your defense(s).