For small bathrooms, the good thing is that since the space is small, it wont cost a lot to make it look nice.
Flooring- One solution is to install tile. If the floor is a single layer of linoleum over the subfloor, you could remove the vanity and toilet, use rock board and screw to the floor appropriately. Then install ceramic tile. If you want the cheap way out, use linoleum tiles which no one uses anymore but hey, it is a rental. The ceramic is extremely durable.
Go online or to ikea and purchase a bathroom set for cheap. If not, piece together a vanity, mirror set online or at home depot