If you are making short or medium term investments, then you may never have to make a principal installment payment, because when you exit the deal, you can just pay back all the principal before the end of the draw period.

Or should it be done at time of install?

YES, there are new rules governing purchases with lease backs, and installment land contracts.

The original electrical would have been installed to run a few incandescent bulbs, a radio or two and perhaps an early appliance and was not designed to handle today's electronic demands.Another thing to keep in-mind, depending on when the property was converted to apartments, is that the conversion may not - quite likely will not - meet current fire codes, which will both impact your insurance rates and your renovation costs when you do undertake a substantial rehab.That gorgeous exterior, with it's clapboard/shakes (or era brickwork) and elaborate trim will be high maintenance - that does not mean it's not "worth it", just that you need to budget accordingly.Personally, I enjoy performing deep energy retrofits on these old buildings (which can be very solidly built), but it can be an involved and costly experience, hence we are always looking for the unloved and run-down which can be purchased cheaply.If that house has been 200+ days on market - and no other landlord or investor has touched it - tells me there is a problem with the value proposition of the deal.  

This will change the function of the window to a "fixed" non-operable window when installed. 

You can also install the hardware yourself and will save a little bit.I would do wood for sure.  

I had plastic installed on the ground in the crawlspace. 

Ceramic tile is great, but too often it's installed improperly.

It's click lock and fairly easy to install. 

How complex is it to have another water meter installed?