Just can't commit to that timeline right now.

Other option is consulting an agent or broker, but am concerned about committing to paying commissions that he market may not bear.  

I just don't want to tie up someone's time or make an implied commitment until I have a better sense of the market.  

But I think they are less prevalent in the Philadelphia area for some reason.

You are still allowed to reject that unauthorized roommate if you find criminal or other negative findings from the screening.If you decide to approve the new tenant, just draw up a new lease for a 1 year term (or your choice) with the new rent and make sure all roommates are included on the lease. easier that doing addendums for rent and roommates etc. and you get them to commit to a new 12 month lease so you dont risk move-outs in the middle of winter.

Instead get  a longer listing commitment and then if the seller wants expensive advertising you might offer in allowed in your state ( and with your brokerages approval) to rebate their advertising expenses at closing they pay for with legitimate receipts off the commission.This way if a seller pulls off the market,goes with another brokerage mid listing, or tries to cancel early etc. the seller will be out the money and have skin in the game.

I am actively seeking to commit my first fix n flip.

Speaking with a CPA and attorney with real estate expertise before committing to anything would be a good idea.

Apple) who have committed to taking back their products at end of life.

Would be a good idea to talk with a local bank and show them your package/numbers and get a verbal commitment (or in writing if possible) what terms they would offer you.