Great work w Loadster. Didn't know it was a solo effort! I founded another load testing service - loadimpact.com, which is doing very well but certainly not a solo effort and has taken on investors along the way. I'm now trying to build something solo again, and would echo the advice to go for something less technical. Plus do B2B if financial success is important. I have three projects atm, trying to figure out which has the most potential - 2 of them are consumer apps (one unreleased, the other is a crossword game for kids - https://puzzlepirate.net) and one is a technical data storage SaaS for IoT sensor data storage (https://pushdata.io). The latter product is a lot more demanding, from most aspects. A simple and maintenance-free product is worth gold when you're running it solo.