If the mechanicals are near the end of it's useful life be ready to negotiate a lower price or have cash reserves day 1.

Another option is to inspect the major items like roof, mechanicals, plumbing, and electrical ahead of making your offer (assuming you are confident you can get it or willing to risk the costs of said inspection without a signed contract).

This is the space where an investor can continue to grow their portfolio even in this market.Now, if you don't want to do rehab and I don't blame you because I've found out the hard way in past ventures that I really really suck at carpentry and most things that aren't basic mechanicals like HVAC (I was an aircraft mechanic in a past life so I "get" things you can assemble with bolts better than how to cut wood in a perfectly straight line even with a jig), there are options to have general contractors and specialist subcontractors do the rehab for you. 

I currently have one fireplace I’m going to remove the chimney from due to an expensive repair being needed and the mason is going to do work to parts of it then brick up the opening to make sure it can never be used again as it’s just not a safe mechanism any more.

It's like finding a unicorn on the head of a needle buried in a haystack.Targeting the specific question about cash reserve:  ask the seller about deferred maintenance, the age of the roof, and the age of the mechanicals. 

I know that people coming from Real Estate rather than the trades and moving into being a landlord, and ESPECIALLY women, tend to like wasting, ahem, I mean spending money on them, but you should bite the bullet and either find excellent, trustworthy tradesmen yourself (who usually have no interest in working for home warranty wages) and/or learning basic mechanicals and trades yourself, at least HOW to do it even if you don't.

They often outperform individual investors if we exclude owner-occupied financing mechanisms which you wouldn't be able to use at scale with $4M anyways.TLDR:You can invest privately through real estate funds.

You wouldn't just hand a wad of cash to a guy to go down to the car dealer and pick you out a car; you'd visit the dealership, hopefully test drive the car, look up the values in Kelly Blue book, maybe let your mechanic look it over, make sure they gave you a valid title without liens, etc.

Exterior doors sizes (12x12; 12x14; 14x14) and mechanisms (chain, remote)? 

If it's just cosmetic, I'd mask it and bandaid it rather than potentially cause mechanical problems.