How to estimate if a purchase is worth it

[Tony Hale]

        I'm a newbie investor from Northern Virginia looking at Baltimore. I'm not new to homebuying as a primary residence but new to flips that need lots of work. I narrowed the best neighborhoods by driving around town (very true about block by block change...lol). But have a question on steps of making an informed purchase decission. 

         In my past primary home purchases, a house inspector will generally inform me items that need repair. How does it wrk in flips? An inspector tells me what needs work, then I get a contractor to give me estimate, then decide if I want to invest? Am I going to bring multiple contractors to the house before I buy it for estimates or will they be able to quote off the inspectors list? 

         Am I able to put a contingency not only of inspection but also of repair estimates so I can back out if I get unprofitable quotes? Thanks for your input.