What do you find the top 4 biggest challenges with buying properties at tax auctions? 

proper notice to enter is usually defined by the state as 24 hours notice. some states require 48. that is your starting point. that being said, coming through with a high amount of showings can be considered as disrupting the tenants right to peaceful enjoyment of their home. if you plan on coming through with one or two, you should be ok (legally) to give tenant prior written notice and come in regardless of their objections. if you think it may take multiple showings, you are likely better off to work with the tenant to set up a block of time for an open house. in extreme situations, you can consider offering a gift card to a local restaurant or movie theater to get them out. the tricky part is striking a balance between what is legal, entering with proper notice, and what is fair and reasonable, since the tenant can purposely leave the house an extreme mess to make it harder to re-rent, badmouth you to potential renters, and may even try to refuse entry. how you approach will depend on your relationship with tenant.

.- 3-4 units still puts you in the residential category- 5 or more units is commercial residential and most lenders will expect you to have experience and will generally have more restrictions on the lending process- A 10+ cap rate in the Boston area will be extremely challenging to find unless you are planning on a massive value add or redevelopment- No idea what your personal financial situation, but a 3 family in Worcester versus a 20 unit requires a very different upfront financial commitment.

Too many people enter this industry without a plan...they get caught up in buzz terms like BRRRR (which is not a viable long-term strategy either, by the way)...I'd personally be interested in your approach to helping investors realize how their investments are actually performing...and direction about strategies you have seen work to generate wealth. 

I am out of state (in the navy) but looking to find a few partners and MF realtors (it has been a challenge).

I am definitely intrigued by the approach, and would certainly run an additional campaign to try it. 

Not really...I've had trouble finding it...I am trying to find deals that offer at least 10% cash on cash returns and it's a challenge

They were either too expensive or located in a challenging neighborhood.Then last week I received an email from an investor selling an apartment complex.

Generally a bank will not go by the income approach on a 1-4 unit (there are exceptions) so you are counting on the market going up to get a higher appraisal. 

I have a hard time believing that any one would waste time over challenging intent over 1% interest.