I am an amateur scientist who wants to submit a paper to a peer reviewed journal. While I have an under grad degree... it was in business and I have been out of school for 15 years. Do I put my undergraduate university as my affiliation because I was educated there? It would be nice to put something.
Do I put my undergraduate university as my affiliation because I was educated there?
Absolutely not. That could be considered fraudulent, since it would suggest you are still affiliated with this university. You should only list an affiliation if it applies now or applied while the work was done, and in the latter case you should note if it has changed (by including a current affiliation or address).
You don't need to include any affiliation at all. It's perfectly reasonable to publish a paper with a private address rather than a work address, in which case you can avoid this issue. If you don't want to reveal your address, you can always get a P.O. box or the equivalent. The main points are that people can distinguish you from others with the same name and can get in touch with you if needed.
You should not list your current employer unless they are OK with being listed. If the research is not part of your job, your employer may not want to be seen as sponsoring your research, so you should ask if you don't know their policy on this issue.
Affiliation does not mean necessarily an academic place of work. The best option is to just use a current place of work. Write "self-employed" if you do not like the above idea. This would mean that you have self-employed yourself at home to conduct the submitted research. I would not recommend the old place of study, since you are not there, you cannot be contacted there and in the worst case the university may get abused that someone who is not their current or recent employee pretends to be such.