So far, I have a mortgage broker that I have built a healthy relationship with and he plans to help me by also referring me to contractors, agents, etc.

Your agent should be able to get you in touch with a PM, and the PM should be able to refer you to some good contractorsAs for the BRRRR strategy: If you're buying in cash and plan on using delayed financing, then you can only get back the lesser of 70% LTV, or what you paid for the property, including closing fees.

You might see it referred to as "cash on cash".  

No references for you - sorry.

Does anybody here has someone that you have worked with and feel comfortable referring? 

Agents that aren't in that area will be eager to refer you to agents that are.

I also have CPAs that I work with regularly and I’m happy to refer you their way.

I would put heavy emphasis into how you pre-qualify your potential tenants (credit checks, income verification, past reference checks, etc) and you'll be fine. 

The easier option is just to bill back the prorated portion of water/sewer bill to tenant, which is referred to as RUBS.

Then call the local burnham or any boiler rep, or supply house and ask them to cross reference your boiler with an equivalent replacement gas boiler.