Assign a contract to a real estate agent's property on CL?

[Robert Uceda]

I have a situation and need to go the best way to proceed on this?  An 60 year old investor, Anthony, who lives in Tennessee had a family member/friend post a bandit sign near University of Denver campus "need to obtain a house pronto" for his sister in law, who resides in Colorado.  Fortunately, I got a hold of him and he is open to me helping him find houses, and eventually get his sister-in-law to select the house of her choice.  

My goal is negotiate with a seller who agrees to sell a house and ultimately, assign a contract so I can obtain my first wholesale deal. I understand I'm better off search houses marketed on Craigslist (of course those without real estate agent involved), or properties off the MLS, which I may find under county websites - i.e. properties on foreclosure, auction, etc.

Will I be able to still assign a contract for a house on say, for instance, foreclosure (or under probate, other off market scenarios, etc) and still be able to arrange seller financing? 

How do I make sure I still get my $5000 profit for wholesaling it.  Would I need a real estate attorney to expedite this assign of the contract, closing costs, etc.? 

thanks for any input