I recently graduated from a master's degree while working on an interesting but niche intersection of machine learning and biology. This area is of my personal interest and I believe it can impact the world in the future but it is not readily marketable. Therefore, I decided to choose a position in a tech company as a software engineer, with works and responsibilities that are unrelated to this niche area. I don't want to give up my efforts in my previous research area and want to continue doing research as a personal passion in my free time such weekends or when I come home from my daily work (which btw I enjoy very much). I find this idea particularly interesting as I would have more freedom to think freely without feeling the pressure of publish or perish and I think it would make the research even more enjoyable to me compared to when I was in grad school and under pressure. However, there might be potential issues and caveats that I am blindsided to them, so I wanted to ask the people here about the potential downsides or considerations in doing research as a part-time or second career.
Also, even if your daytime work is not related to your personal research, you may either have signed something about IP (=intellectual property), so that your employer feels that they own essentially everything you do that is even remotely related to your job. I'd think you should look into this, discreetly...
The main issue I can think is time. Other people who will be working on the same research field will spend their full working week on the topic while you will be working only in your free time (weekends etc.). So you will be progressing very slowly and there is a high chance that you might get scooped if you are working on some hot research topic.
All that assuming that you have some average productivity aptitude and you are not some productivity beast that is able to finish up work in 1/10th of time than the rest :)
In addition to time constraints, you'll want to try to collaborate with people or professors from your institution. It is pretty difficult to do good work alone, especially in computational fields. One benefit of doing research on your own time is the flexibility to explore areas that may not have immediate funding or interest, but could be impactful.