I am nervous this will put us in a bad position for March. 

If the price to replace is within budget I'd do it because you're putting out a newer/safer/more reliable product.2) Cost to replace the entire systems is tough to gauge without knowing the building size and style...

Don't take it for granted and don't put all the eggs in the same basket.

Yes, 0 cash flow is a negative CoC return, but, if you're just paying costs to close the loan, you keep all your cash and put it somewhere else. 

As to the actual construction, time can be saved by ordering materials in advance and put in storage, having multiple crews going at once and having tight timelines. 

I want to set up for a 1031 of a set of apartments that are in a trust and put new apartments into an LLC.

Put 15% down total PITI payment was $1,750.00.

Borrowing from the equity must be done wisely or you will end up with negative cash flow and at high risk due to over-leveraging.NOTE: I use interest rates much lower than they currently are in 2024!

I am working toward my RE license and would like to begin as an agent by the end of the summer as a part time job along with my W2 so that I can put any income from that into paying down that HELOC and putting more cash aside for the next possible deal.I'd like to have 2-3 more rentals within the next 5 years so that I can transition from my W2 to full time real estate (is that realistic?

You will then have a few options with that rent money....you can put it into principal or you can start saving it to purchase yet another property.