He extended himself to be there whenever I had questions and he paced me all the way through a very smooth transaction.

The main benefit is that they extend the life expectancy of your property.  

You shouldn't have a problem with the shelf if it is mounted on studs and the supports extend out to near the end of the shelf (far side from wall). 

I had the opportunity to get out as my contact was up last may but choose to extend for a bit, because right now I am able to juggle both so why not keep double dipping and put the extra income towards future deals. 

Background: It was previously listed for nearly 2x this amount but sat on the market for an extended period. 

Should I extend timeline for deposit and use cozy to collect, so the tenants get familiar with it now?

You've certainly come to a great place to extend your knowledge.

Also a roof extends a few inches further then the floor plan, also the roof needs double layers around the perimeter of the roof and on the ridges. 

The lender, depending on the circumstances of the deal, will usually charge an additional % to you in order to extend the term of the loan.

A partner might be willing to add to your cash pool for an agreed upon return or may extend their capital for the down payment while you use your funds for any needed improvements.