You absolutely should lend our your own capital before lending out other's capital. There is a lot of risk and variables to navigate and sort through and I'd much rather learn on-the-job with my own capital than risk others. There's a huge difference between raising capital for a fund (typically a security) and raising capital to broker PML loans through (also known as private placement and in some states not considered a security and in some it is). Also, fractionalizing loans (putting more than 1 lender named on the loan can also be deemed a security in many states. For example, in WA, a debt fund is a security and I have factors to think about when raising capital - 506c has less restrictions than 506b). As other PML veterans here have mentioned, a fund is expensive just to get started. The other part you'd need to think about is deployment of capital and the rate of return you'd give your passive capital investors. When you broker/private place loans, there is not a cash drag to you as the broker in between loans. When you have a fund and a loan comes back, you are still obligated to provide a return to your LPs whether or not the funds are redeployed or not. Also, i would say smaller funds can be economically more difficult with a high expense ratio under say 5-10M AUM (assets under management). It's doable but you'd be doing a lot in house for fund administration and that is a ton of risk. I much prefer outsourcing fund administration, legal and taxes to ensure we play it right and safe. I don't need any agencies coming after me.
If you haven't already done so, you can pick up a copy of my book Lend to Live: Earn Hassle-Free Passive Income in Real Estate with Private Money Lending off the BiggerPockets bookstore. It won't cover how to set up a debt fund (that's advanced level LOL) but it'll cover all the key considerations you'll need to take when safeguarding your own capital. Let me know if you have questions!