1) Income Taxes (if you're going to claim the rental income) and Property Taxes

2) Repair/Upkeep Costs

3) Having a STRONG lease for late payments, pets, due dates, security deposits, what the tenants and landlord is responsible for, etc.

4) Screening Tenants (unless you don't care about their background / if they're reliable, etc)

5) Setting a competitive price (room prices may vary based on room size / how many people are sharing a bathroom, etc)

6) It's most likely a good idea to ensure your tenants have rental insurance (in case something is damaged of their caused by you, and vice versa) 

One of the most important things to consider is that you need to make a profit on your rental home. I overheard someone talking the other day about rental properties and he thought an extra 1-200/mo was a good idea, I strongly disagree. You need to be making 20-30% in profit (per home, not tenant)) to save for potential damage to your home. If you need to replace your roof and it costs ~$10,000, then it will take 50 months to pay for the replacement at $200/mo in profit.