One of the most stressful things for me as a landlord is dealing with feuding tenants.

It will cost you more in time, effort, and stress than the Earnest Money is worth - unless it's a very sizable sum.Based on what you have reported, you most likely had an existing sewer leak you were not aware of revealed by the Hydrostatic Test.

The lender is an important part of the team in any transaction, I really stress this with each of my new clients.  

@Frank WongHi Frank, I agree, every property cash flows when you pay all cash for it :) and a lot less stress when problems occur.

Getting to closing always has some stresses involved.

Typically rental rehabs are less stressful than flips since you have to be so detailed oriented with flips so your house is actually able to sell.

Its obviously a busy and stressful time. 

@Julian Hendrix Nothing wrong with that strategy as long as it isn’t causing too much stress.

Single families are great for many reasons(usually less stress but less cashflow too) single families usually have a lower cap rate than multi units(more money but slightly higher stress). 

@Jeremy Taggart That was weighing heavily on my decision to sell or renew my tenant’s lease last year and, in hindsight, selling was probably wiser. 1031 exchanges get stressful if/when you can’t find the right deal and I have only worked on other investor’s 1031s as a broker.