Im a P1 right now, but I worked in an inpatient pharmacy for 4 years before starting pharmacy school. I currently still hold my position. My director actually offered pharmacist positions to 2 of our P4's that were getting ready to graduate. They had been working there since their P2 year. So no residency required, just being well-liked by the pharmacy director and being an intern there for so long.
However, one poster was correct, they won't be able to be on floors doing clinical work. Not yet anyway. Just down in the main pharmacy checking orders and doing "tech" stuff, handling medstation problems, etc. Secondly, I know when hiring new pharmacists, our director only wants people that have either been in the hospital before or people that are coming out of a residency(The director would tell us why she would and would not hire pharmacists).
So I think if you don't do a residency, it might be difficult to get in if you don't have relationships already built with hospital managers/directors and they'll bring you on b/c they know youre smart, work hard, and you have a lot of training potential. Not impossible if you don't have either, you just have to find the right place to give you a chance. We have a couple of pharmacists at my hospital who didn't do residencies, and actually do clinical work. Big research hospitals might be hard to get into without a residency. Mine doesn't even have a Pediatric ER or trauma center, so that's prob why our director was a little more lenient(in the beginning, we're growing, so I think that's why our director is getting more strict on residencies).