In southern CA, even garage conversion ADU additions are typically costing more than the value added.  

@Franklin PerezGetting your real estate license can be a smart move if you want MLS access, networking opportunities, and savings on commissions, but it comes with costs and disclosure requirements.

Next up is a huge financial hit: closing costs.

If one tenant has been in there for that long, there will also be some serious capex and turnover costs.

To qualify for a loan, focus on having a credit score of at least 620 (or 580 for FHA loans), keeping your total monthly debt under 43% of your income, and saving enough for a down payment and closing costs—about 5-10% of the home's price in total.

Is just the fact that no garage could be a no go for some buyers enough to build it even if it only raises the value by the actual cost?

In short, I can afford the additional $1100/mo cost of a second house, even until I rent it out.I have around $35K in HYSA and emergency funds that I could use for a down payment, but that's less than 20% which would be required for a conventional loan, assuming full purchase price.

Property taxes and insurance costs are best obtained through local county websites or reaching out to insurers directly for quotes specific to the area.Tools like BP Pro and Reventure can be helpful for an overview, but it’s a good idea to validate their data against primary sources to ensure accuracy.

This approach ensures realistic pricing and helps avoid unexpected costs later.Good luck!  

There are ways to mitigate the costs and protect yourself to the extent possible.