So therefore we're plannig to go with a single family home, but thinking to turn the garage into an efficiency and rent it out, I don't know if this is illegal, or is there any other recommendation?

If so, will the agent be less motivated to help us?

In addition, a helpful thing to know is more about the seller and their motivation for selling.

Also – side note, I have been a bigger pockets fan for 3 years now and it has motivated my wife and I to FINALLY purchase our first investment property last year.

In general with house-hacking I'll always prefer small multi-families because it bakes diversification and efficiency into the purchase, giving you slightly more levers to pull and security in the investment. 

I've ordered the BRRRR book from BiggerPockets, and I've listened to BP Episode 327 where they do a BRRRR deep dive where David softly advised against this (@ 1:19:48 in BP 327) because it wasn't efficient, but I wanna learn more and see if it would be a good-enough way to get into real estate for someone in my position.I'm estimating that by the time I'm ready to buy--November 2022--I'll have $70,000 (not including my emergency fund) in cash for everything: cosmetic-only renovations, initial down payment, closing costs, etc.

Stick to fundamental buy-and-hold real estate...noting glamorous or fancy...If you have safe, clean, and appropriately priced units...focus on C-class value add, and maybe consider working with the local housing authority to accept housing choice vouchers, you will have long-term occupancy, debt paydown, and equity build for life.Investing is relative, and I doubt your main motivation to invest in RE is to contribute to the list of "25 fastest growing cities in the US"Best of luck

Are you paying the utilities, if so install energy efficient appliances/LED/low flow water spiciest.

Improve my processes and make me faster and more efficient, I think what I am really looking to do is flip here in San Diego but take the proceeds to another market that I can find cash flowing properties. 

Lots of opportunity in this deal by just adding management efficiencies.