Ordinary loan with a pledge of own property
This, of course, is hardcore and the risk of losing everything if the startup does not take off. But if you have confidence in your abilities, this option is, in my opinion, the most correct and will seriously raise the credibility in the eyes of investors at further stages of finance your side business.

I myself, as a managing partner of a small investment fund, all other things being equal, will choose the guys who put their money and assets on the success of the project.

In this case, they will, firstly, have a much more responsible attitude to costs, and secondly, they will fight for the project to the end.

If the amounts are large, and the project involves the acquisition of fixed assets that can be used as collateral, it is advisable to consider project financing programs from banks. To do this, you will need to protect a detailed financial and business plan in front of the bank.