With cha1 and 300speech + Magnetic personality it is possible to get 3 mercs. However you can't lead them on worldmap so you're stuck in the place you bought them. Taking drugs helps however.
In addition I couldn't tell the mercs to stay in location (is it even possible?) so if you truly are out of drugs and buy those mercs, only way to get out of town is to kill the mercs or disbandparty.