Along with paying all of the utilities, internet, cable, yard upkeep, and snow removal.  

We do have some areas that are owned by the HOA, they are actually protected tree zones that require some upkeep.

I really believe that you need a strong local real estate agent who can help guide you with not just financial information, but also contacts who can help with the maintenance and upkeep of the property. 

Check out David Greene's BRRRR book - its worth its weight in gold!

Green Street Commercial Property Price Index places more weight on high-quality properties, e.g. a New York skyscraper has a much greater impact than a suburban strip mall.

A good financial advisor is worth their weight in gold. 

If you can use the weight of your loan paired with deposits, this may sway the needle.

Would a fourplex be double the headache to manage and double the cost of upkeep and repairs than a duplex?

A phone call holds zero weight.

You'll also want to ensure you have a good property manager to look after the upkeep of the property if you are not there to notice anything deteriorating or which may need attention.This article goes into a lot of the considerations about whether to form an LLC or not: https://www.mmpph.com/wp-content/uploads/2019/04/May-2019-newsletter.pdfCreating an LLC in California would cost you a minimum tax of $800 every year.