Should I build a 4th room to my Rent by room house?

[Julio Franco]

I have a 4 bedroom, 2 bath and 2 living room home. 1 bathroom is private, inside room. The layout is weird and has 2 living rooms.

I live walking distance to major hospital, and minutes from colleges and universities. 

Monthly PITI payment: $ 2,780.00

Equity in home: 250k

I want to move closer to my job as I am driving 40 minutes each way every day and going through a divorce so I don't need that many rooms. I can't purchase near my job because homes are crazy high there. 

My plan is to rent out my current home by the room, fully furnished and move my self and kids closer to my job by renting. Kids already attend school near my job. After around 6-12 months of renting I plan on applying for new loan to purchase a duplex and primary residence. Even if I move another 40minutes away again I would be okay with that.

If I rent my house per room at $750 each room plus $850 for room with private bathroom I could make $3,100 plus the savings from gas, time and renting since rent will be cheaper than my current mortgage. 

I spoke with a contractor that has done jobs for me before and he quoted me $9,000 to turn 1 of the living rooms into a room and add 1 extra bath without permits. 

My question is; 

1. Should I invest the 9k to get an extra $750 per month? But what if I want to refinance or sell in 10 years, the unpermitted room with bathroom might create a problem? I don't have any plans on doing this but I am thinking this might be a good idea if I come across a better  deal in the future. 

2. Should I create 1 extra room without the bathroom? This would run me around 4k to 5k but this means there will be 4 rooms for 1 bathroom.