mold issue

[Gregory Massi]

I just purchased a condo last week and turns out I have a mold issue in the bathroom - seems like its only minor as its only on the surface of the sheetrock and trim but its musty smell is strong in the bathroom and master bedroom. I would like to get rid of this smell before i rent it out. I don't think any of the pipes are leaking but should i remove the sheetrock to confirm? Also what is the best mold remover? Would an air purifier help with the smell?