just to be clear, hiring a patent attorney to do some preliminary infringement/novelty research is a good idea, but one should NOT expect the results to "verify you are not infringing on any entity's patent". You could hire a whole herd of patent lawyers and still not be sure that you won't infringe either an issued or pending patent. And you won't know about provisional patents because they are not published. That's just the nature of patents and our patent system. There are far too many claims in far too many patents that have been issued as well as those that are pending that some troll or patent owner could decide they want to use to make your life difficult. Many of these claims are hidden in other patents that on the surface having nothing to do with the space you are in. A good patent attorney or agent should be able to give you an opinion as too how "crowed" your space is, i.e. "are there lots and lots of issued patents that read directly on or around your subject matter" and "is the space heating up given the number of recently filed and unissued patents pending around your space" as well as "who seems to think your space is interesting based on what companies are filing patents and claims in this space". Someone could have filed a provisional patent application yesterday that reads exactly on what you are building and you will not know until or unless it is turned into an actual application and published and possibly issued 2 to 10 years down the road. If the space seems to be heating up that could be a good thing - someone may want to acquire you.
It is good to understand 'patent strategy'. I am NOT a patent attorney, but i have a few patents and i've driven this road a bit. For the most part today, patents are seen as bargaining chips, or more accurately, ammunition. The more chips/ammunition you have the better, in general. Even if you plan to never start a war, having some defensive weapons is always a good idea. If you are small and you infringe a patent (or claim) owned by a 'troll', for example, they likely won't sue you because you have no money - they aren't interested in shutting you down, they want money. If you have patents You may never intend to sue anyone for infringement, but then again you, like Apple, may change your mind when competition heats up. You might use your patent portfolio more as a defensive weapon than offensively. remember back in 2012 or so when Yahoo sued Facebook over patent infringement? it was just before FB was to go public. FB went out and bought about a half Billion dollars worth of patents from Microsoft (and they continue to buy) and all of a sudden FB and Yahoo settle and announce a "new and improved partnership". The moral of this whole story is that startups are risky and risk comes from all angles. Is there a risk that you might get sued for patent infringement some day? yes, if and when you become successful, but not too likely before then. Should you consider building or buying your own patent portfolio? yes, but unless your success depends heavily on patent protection (the prescription drug or biotech industry for example) then i would not commit a large portion of my scarce funding into patents just yet.