Probably not an issue at this point if your portfolio, recommendations and grades are good enough.   Once you get in somewhere, make sure you get some work experience on school vacations.  Getting an MArch and still not having any internships really will hold you back.

Zero. Admissions is not trying to build a classful of experienced professionals - if anything, first semester will be all about starting from scratch for everyone, including the seasoned students/pros who sometimes have a harder time ridding themselves of work habits.

Nobody expects MArch I applicants to have any experience in architecture. If you do have some, that's a bonus, but if all you have in your portfolio are the custom surf- and skate-boards you've been building (this was someone I actually knew), that's fine - they're looking for general creative ability, and your personal statement explaining why you want to get into architecture will probably carry the most weight.