That’s illegal, unfortunately. Only qccredited investors can invest into private companies. There should be a lower limit on that rule, say $100 or something, so naive investors could invest play sums in potentially shady stuff. But there isn’t, so you can’t.
Maybe the same as with drugs in sports: Self-experimentation can be an expedient shortcut, and scientists are often very competitive people. If results obtained through self-experimentation are rewarded, many scientists would be tempted to do it. Contrary to doping in sport, however, in science you need to at least do something different each time for it to be publication-worthy. That institutes a big skill floor and considerable risk, so I think a self-experimentation epidemic is unlikely. Generally I still think self-experimentation is good, precisely because it’s such a shortcut.