The biggest drawback for most people is that you normally can't get into the property to have a look before your purchase. 

@Mary Ann There are drawbacks and advantages to both.

Rent by the room models have seen some draw back and if the current hesitancy trends endure, having an alternate strategy for weathering this or any other future economic storm could help tremendously.   

However it has some drawbacks as it has a cost to set up and maintain.

It may be better simply to raise rent to a level that you find acceptable to mitigate what you perceive to be their drawbacks as tenants; although in a multifamily, you may have to watch out for the appearance that you are treating them differently than their neighbors.

What are the drawbacks when it comes time to purchasing what will more than likely be our new primary?

I know there are drawbacks but it is a reliable income source especially in this post COVID environment. 

I was hoping for some guidance from everyone on which is the better strategy, and maybe point out some things I may have missed.Here are my goals:- purchase 2-3 properties a year to hold and rent- appreciation is nice but not a must have, focusing on cash flow and debt paydown as the benefits- open to possible rehabs/light cosmetic - I want to start slow with my first property, but if things go smoothly I would be ready to rinse and repeat when the right deal becomes availableSCENARIO A- use HELOC for the 20% down payment and then take out a traditional mortgage for the rest- POSSIBLE DRAWBACKS - not sure where to get $$ for the rehab if needed.

For an investor looking for cash flow, would there be any drawbacks knowing they aren't purchasing the land?

I mean are there any drawbacks or concerns an investor might have when choosing to get started with this path?