You typically need at least 20% down on loans so if you have little to no money or don't want to put your own money down, you probably won't get financed.
If you have a 401k with over $25k, you may be able to use it tax free and penalty free.
Also, talk with the owner and see if you can manage it until you build up a down payment. It never hurts to ask. Then if he sees you are doing a fantastic job, maybe he will finance you.
Otherwise, try to borrow from friends and family and let them be partners but have a buyout plan.

Web reference: http://www.pittsburghbusinessesforsale.com/financing

Who gave you cash flow figure of 150k
Was it the seller or his broker
Remember that 80% of the time these 'cash flow ' and profit figures are wildly exaggerated puffery at its finest
In term of financing this is a non starter in today lending environment
if you.can't risk your own money why should someone else risk theirs

Hey Brenden, send me an e-mail to discuss.
vigasimple@gmail.com isaiah