Meeting that 15K limit will be the biggest challenge. If you are willing to buy an airplane kit in pay-as-you-go stages, you would be hard pressed to find a better value than an LSA compliant Van's RV-12. Here's why. Thanks to computer generated advances in design and manufacturing, the kit parts are delivered to the builder predrilled which is a HUGE timesaver and the advantages that brings to the new builder with little skill or experience cannot be overstated. Since the RV-12 is mostly assembled with blind fasteners set with a common hand pop riveter, traditional sheet metal skills are greatly mimimized. Typically, you pull parts out of the shipping crate, cleco them together, ream to full size, disassemble, debur, reassemble, then rivet it all together. No welding skills are required either because all welds are completed at the factory and those parts are shipped to the builder with a powdercoat finish.
Another major construction plus is this. Learning new electrical skills is also minimized. There is no waste or needless expense buying wiring components that you may or may not need. That is because the wiring harness for the RV-12 is completely preassembled and when matched with the instruments called out in the builders plans is about as close to being plug and play a solution as you can get.
As an EAA technical counselor, I have inspected an under construction RV-12 project and came away very impressed with the degree of sophistication written into the builders plans. It contains many illustratioins and is written with clearly explained "bullet points." You simply check off each bullet point as you proceed along the assembly process. In no time at all, that collection of parts will take the shape of a real airplane.
Finally, builder support is widely available and is part of quite likely the largest single group of aircraft builders in the entire experimental aviation homebuilding community. By joining the RV community, especially Van's AirForce (VAF) you will quickly discover that there is not a single challenge you will face that has not been dealt with by someone before and the solution shared among the VAF membership over and over again.
There are some good airplanes out there that meet your performance specifications and the RV-12 easily exceeds many of your stated requirements with a speed similar to that of a Cessna 172. There are many things the RV-12 with its set of quickly removable wings can do, but the one thing the RV-12 cannot do is meet that 15K limit.