a club can bring over any player it wishes to for spring training games, and traditionally does so for every game. if you view the pre-game notes, you know who those players are. i visited maryvale last year. the minor league playing fields are farther away to the south from the main complex, and have limited public comfort station facilities nearby. if i recall correctly, there was one facility (used by the players and the public) within the vicinity of four or five playing fields on the south end of the complex. but when a non-roster player in big league camp, he's working out on the main playing field, which is adjacent to the new, state-of-the art facility. and he does get a per diem, and he definitely gets better meal services inside the clubhouse. minor league players don't get paid during spring training (they start getting paid opening day). and i believe that they are responsible for their housing while in arizona. it's not uncommon for 8, 10, 12 guys to be living under one roof at a short-term rental house. it's unclear if that non-roster player under a minor league contract is paid during spring training, or if his pay starts on the opening day of his minor league season, like everyone else.