After all, anything the seller pays for, is something you don't have to later.You need to carefully measure what you ask for against your relationship with the seller.

We are not sure it is because the electricity is off so the sump pump is off, or if the sump pump was on in the first place it still would have flooded.What kind of measures can I take during the rehab to prevent any future flooding, besides a working sump pump

Either way, I would first look at the amount of available space in your rear yard (measure the lot width, which is probably 50' or so, and the distance from the rear property line to your house, which is hopefully >35') and see if you even have the space to build a 1 or 2 story unit that has your desired bed/bath count. 

Period.The KPI I will typically measure for SEO are:1.

Have you read the book,  "What every real estate investor needs to know about cash flow...and 36 other key financial measures" by Frank Gallinelli. 

Are you referring to a standard property survey for measuring a lot?

Btw that’s def a metric I measure....how ridiculous ppl who are good at what they do think of what I plan.

You can install either multiple smaller systems or a larger, multi-headed (multi-zoned) system.Regardless of the heating or cooling system you install, your biggest bang-4-buck will come from air-sealing and improving the building envelope ... this can be a simple as replacing weather stripping on doors and windows and caulking trim to adding additional insulation to the exterior (or interior) of the wall assemblies / attic space and replacing windows and doors.You should probably start with having an energy model {aka heat loss analysis} performed on your house which will identify the current energy losses and the measures you can take to improve the performance.

My advice though, make sure you read through reviews thoroughly and measure the dimensions of what you're purchasing.

We will pressure test the entire structure 3 times during construction and once at final turnover to ensure our air sealing measures were successful.