How it works in LCPD:FR is you start off with a baseball bat (certain mods change it to a police baton), a pistol and a shotgun. You can use weapons from dead criminals, or that you spawn in with a trainer. In LSPD:FR I guess we would start with a proper baton, stun gun, pistol and probably a shotgun. More weapons could be picked up from criminals or spawned in. I don't think buying weapons would be a feature, especially how you most likely can't save the game as a different ped or it'll cause issues like it did with GTA IV.