These projects can be a minefield if you’re not careful about scoping them out from the start. Almost every side project turns into 2X to 10X as much work as people estimate from the start. Don’t get locked in to a fixed bid for open ended work.

If possible, ask around your network for what people charge for freelancing rates. The answer varies wildly depending on skill level, frequency of freelancing work, and range of services offered. For app development, I personally know people charging $50/hr and others billing $200/hr for what I consider to be equivalent work.

Most freelancers will raise their rates until the clients decline contracts and then back off. If this is your first round, you’ll have to guess a bit and then re evaluate the contract later.

Finally, keep in mind that this will become a drag on your time and energy. Earning $10-20K on the side is great if you have idle time and extra energy, but if you find yourself too drained to do your day job well then you’ll need to evaluate the possible career impact. Don’t miss out on promotions or new job opportunities because you’re too distracted chasing small potatoes side projects. If money is the goal, you can probably do better by actively seeking a higher paying day job. On the other hand, I’ve gained valuable experience and networking from freelance work, so consider the intangible upsides as well.

All I know at this point is that they've had a younger guy build an app for them in Java and it doesn't work as well as they'd like it to. They said something about it outputting to Excel, and that right now they can watch it putting the data on the spreadsheet in real-time, which isn't desirable. Also, there was something about it being manual rather than automatic.

My work colleague has sold me to them as a Java guru, which might've been true 6 or more years ago, but I haven't used it in a while. They still have the original developer, but they think I might be able to teach him a thing or two. My Java experience was mostly web applications, so it's hard for me to say whether I'll have much value to add or not before looking at it.

I do well enough right now that I don't plan on chasing side gigs, but I'm not afraid of giving this a trial run.

I know it’s not the same but I make word clocks[1]. They are limited edition and (I think) high build quality. I’ve found one brand of high end word clocks. Mine are a different design but at least equal finished quality. I charge on par with those. I don’t sell a ton, but I don’t spend a ton of time. The time I do spend on selling works out to a high enough hourly rate that it’s worth it to me to give up other activities (ie opportunity cost).

1. Www.finewordclocks.com