Buying my First Home and House Hacking

[Mitchell Zobel]

I am a 23 year old single male looking to buy my first home using a conventional loan with 3% down payment. The home is a 2 bed 2 bath with the ability to easily create a third bedroom, which I plan to prior to moving in. There also is a 4th room that does not contain an egress window. My plan is to live in the 4th room while renting the other 3 rooms out. My question is when it comes to renting out rooms to friends, should I still have each tenant sign a lease agreement and treat the property as a rental? Or should I just give them each the $300/mo price tag and a date each month to pay by? It's also worth noting that I travel a lot and will not be in the home most week nights. The possible tenants will likely treat this home as their own, while I am there only a few nights per week. The majority of furniture and utensils will all be the tenants possessions as I have very little. 

My second question is after a year am I able to turn this property into a rental and purchase a new primary residence for myself? That is the general rule I have gathered but would appreciate clarification!

Lastly, if renting out my primary residence, it's my understanding the income from the property cannot be used in the calculation of my DTI? After the one year period am I then able to include the income in my DTI? Or would I have to refinance in order to include the income? That's a lot of questions, but if you have any insight on any part I would greatly appreciate the input. Thanks in advance!