The first question you need to answer is whether or not you plan to inspect with your phone. By that I mean use software on your phone to take pictures and make inspection entries at the time of inspection. Despite having such software I still find it easier to take pictures with a camera and complete the report in the office.
One thing I have found helpful is to track calls and update my calendar with wifi software. I don’t particularly trust someone else to store my data (the ‘cloud’) so a fair size memory card is good.
Also if you do decide to use your phone for inspections, you might also use its GPS capability to get you there. Don’t forget to have an adequate car charger. Use it with the GPS while driving so your battery doesn’t suddenly die on the inspection. If it does die make sure you have a backup battery that is fully charged to continue the inspection (I think I bought one at Bed Bath and Beyond).
Having said all that my phone is a simple Samsung SMJ327 you can buy outright for about $100.00.