I've started looking into creating a pest control business, or maybe renovating furnitures I find on the street. Let me know if you have other ideas for senior engineers.
I would love more existing or recently ex- software engineers to share what new activities they have been taking up for living and that have been going well. I am certain that there are niches where a refined systematic thinking that many software engineers have could be a big advantage. However, it's expensive and risky to start new businesses in areas we don't have any experience in.
FWIW - I think the small business market is actually very suitable for former SWE's. The capacity to troubleshoot processes, variance, bottlenecks, etc. is what turns a mom& pop shop into a regional chain.