Depending on the age and condition of your property, you should ideally be setting aside 3-7% of your gross potential monthly rents (occupied or vacant) to repair or replace Capital Expense items. 

No overhead wires means no downed wires that are your fault or expense to replace. 

Trying to replace the aged heating furnace in my property.

Challenges - We started with a rehab team that was screened and on board, but finding replacements and additional contractors was a challenge at times.

You should always ask for a "Reserve Study" to determine what the HOA is responsible for and how much it cost to make replacement or repairs to said items. 

They replaced and brought two water heaters up to code.

The 3 biggest components of your closing costs are you insurances... title insurance which is usually around $1200, and then your homeowners and flood insurance.

The “guts” of the house have been replaced in the past ~5 years in preparation to sell the property.

Also, some will do Replacement cost while others only do Actual Cash Value for how they payout on the loss.You should probably seek quotes from an independent agent.

When was the HVAC, hot water heater replaced?