You want to buy more rentals, so why not use the money to get started on that sooner rather than later? 

I do have an empty lot next to my current SFH , doing nothing (but costing me money to mow :)) my thought was to build a detached guest cottage to serve as an overflow for guests or it could also serve as a seasonal / monthly rental.

I want to start taking steps to make that a reality.

Started chirping them at the squash tournament.

I suggest you suck it up and cover these costs and just build these costs into the rent. 

Most buildings of this size often only appear on the website of the listing brokerage. 

Prices and rents continue to increase steadily.Sales - $/SqFt by Month(Click to enlarge.)The median sales $/SF was up 9% YoY and 6.7% YTD.Rentals - $/SqFt by MonthRents rose 4.3% YoY and 6% YTD.The Market Remains HotFollowing the rapid inventory decline starting in Q1, the number of days on the market for sales remained below 17 and for rentals below 19, indicating strong demand for both.Sales - List to Contract Days by MonthRentals - List to Contract Days by MonthRental trends tend to follow sales.

But the simplest test is going to be to turn on the water and see where it starts gushing.

I have begun reading books and articles  trying to educate myself before I start this journey. 

Or build something?