A pair of 5W 2m HTs should be able to maintain communication over 15 miles if there is clear line of sight. If there are significant terran features or structures blocking the path, you're out of luck. That's why we use FM repeaters on VHF and UHF. The repeater is installed on a tower or building on high ground so that it is easy to maintain radio line of sight to almost any location in a wide service area. I've used our club's repeater with an HT from over 30 miles away to talk to someone with a mobile rig 50 miles away in another direction. I live on a hill and can get into repeaters that are on high ground over 60 miles away while sitting in my living room with an HT.
Almost every populated part of the US has coverage by one or more 2m repeaters. Get a copy of "Ham Radio for Dummies" or the ARRL book "Getting Started with Ham Radio" and use it as a study guide. You'll find a clear explanation of HTs, repeaers, and how to use them.
If there's a club in your local area, try attending some meetings. You'll probably meet several hams who will be willing to help you get licensed and on the air.