If you are looking at a house that needs work cosmetically and you have little experience, it is likely the mechanicals are older too and that's where you get killed.

I may not have been clear enough: the ADU is already built, we will just need to do cosmetic fixes (literally painting and rebuilding the shower just because it is super old).

Were they mostly cosmetic rehabs or was there anything big you needed to do at the outset? 

I know I can probably house hack my way to 5 properties in 5 years, but I assume I'll probably learn more efficient and aggressive ways to scoop up more properties as I complete my 2nd-3rd house hack, so that I can start picking up more than 1 property per year.I don't want properties that will take a lot to fix up, I'm fine with cosmetics and do-it-yourself type things.

It looks like most of it was painted over and/or given a cosmetic "covering".

Once you buy your first duplex, it is best to do a light-cosmetic SFH BRRRR or duplex BRRRRR.

I want to scale to maybe 10-20 rentals and $25k-$75k a month using rentals, wholetailing and maybe a cosmetic flip.

If this is primarily cosmetic repairs, then you will be ok.

According to my estimates and the fact that only minor cosmetic upgrades are required, the all in cost is 30k.

I would suggest doing a very cosmetic first flip.