you can put your deposits at as many schools as you have $$$, while some schools ask for as little as $250 some like BU will ask $3000. May 1 schools suppose to share info who deposited where and theoretically people could be dropped out if they do not play nicely...
once admitted you will receive package with info "what when and how"- dorm application, parking space, vaccinations. You will have to get Hep B which is series of vaccines. You could start earlier to get all 3 rather sooner than later but overall you will have enough time before you start working with patients. If you have been vaccinated, showing titers won't help as you still have to show proof when and where you have been vaccinated.
People usually have facebook group formed to share info. Some schools will have boards where you could get in touch with present students to find roommate or living space.
If one waitlisted they could also ask to put down deposit which usually stays there and is used as deposit if you do get admitted.