For your first question, if your goal is to use the equity in your current home, a HELOC could offer you more flexibility to tap into your equity when you're ready.

For financing a portfolio of 19 properties, consider seller financing, which may offer flexibility if the seller is open to it.

If you can run a successful arbitrage business you can make a lot of money, and if you hedge your bets and put that money back into owning more assets then why not?

There are many advantages*  A customizable fund provides amazing flexibility to raise equity or debt or even a combination of both. 

Are there specific lenders you recommend for more flexible terms despite credit challenges?

And, I'm not against the flexibility of the relatively cheap Credit Card call a HELOC.But please don't try to confuse "flexibility" with "pay down".

If you’re just saying the survey cost of getting the existing building layout documented is too much, you might be able to get creative and avoid the costs, but it’s not a great bet to make. 

Their influence is felt in the increased accessibility of capital, the acceleration of project timelines, and the introduction of more flexible financing options.

Often times inspectors overlooked them as they are very small and minor but as you can probably already tell, they are extremely important and prevent water intrusion.Your best bet would be to contact a very reputable Siding/roofing contractor and have them go through the entire property and put in the proper drippage flashings seals and caulking necessary and have them insure the work. 

We just found her through UpWork.com which is probably your best bet for quality VAs.