Savannah all I have is one of my houses has a damaged roof, that's it and feel fortunate.

If not, I suggest waiting until you do.If you use up all of your equity on your current home, rent it, and then need a new roof or boiler, your attempt at your first door will go sour.

How to know when is time to replace the roof. 

Now, you have an appreciated first rental that’s hopefully generating cash flow, and a multi unit that provides a roof over your head and 1-3 units paying down your mortgage while all units continue to appreciate.

Multiple times projects took so long to get started or to get an appropriate bid, I ended up having to handle it myself (ie. roof replacement, unit turns, etc.) 

Now, despite this it is profitable, but key aspect is the special annual grants they get for having that % of total portfolio as subsidized housing.

HVAC duct work insulation is also deteriorated.No vapor barriers installed eitherSome fungi/mold growth notedPlumbingMultiple small leaks under sinks and from bathtub and toilets.House has Polybutylene plastic plumbing which is dangerousMain shut off valve is damagedElecticalSome small exposed wiring and bad splicing.Whole house has no GFCI's or grounding outletsInteriorMoisture spots on ceilingExteriorLose Vinyl SidingDoor Jams and Window trim have moisture damageDriveway need replacementRoofingMinor leaks noted in atticRecommended to replace roof covering, but not whole roofSome fungi growth noted in roofSo some of the question I am trying to tackle with this work is:How much should I budget for the main issues listed? 

I tried to estimate what a GC might cost in my calculations, but I have an uncle who does roofing and cousins with window installation and landscaping businesses, so I believe I can save some significant costs through their help and guidance. 

Your HOA will likely keep increasing and because of the excessive heat, roofs get replaced more than in other areas and if the HOA is not super liquid, that will come back to you in the form of an assessment.

Your first is already risky enough since you lack experience, combine that with 100% funding and the risk is through the roof.