How do you plan on acquiring capital as bank lenders tighten up?

Canada Mortgage and Housing Corporation (CMHC) insures mortgages with less than a 20% downpayment, and they are tightening up the qualifying rules.

With all of the uncertainty that COVID-19 has brought during this time, I understand that many financial institutions have tightened their lending criteria to those looking to obtain such financing. 

With the tightening of lending requirements, seller financing (creating notes) will probably be a popular option as well.

Rates are low but liquidity is tightening up.

If he stays, be sure you stick to your guns, and then take a good look at the situation when his lease comes up for renewal.I would also take some time to tighten up your lease provisions a bit if that is also a source of the confusion.

And what if mortgage underwriting guidelines tighten up (they already have, to some degree) and call for additional reserves and a higher credit score?

The challenges will be the recent tightening of qualification standards, but if you've got some reserves, proof of decent income, and a credit score above 700, you should be fine. 

First off wasn’t 2008 simply an outcome of poor underwriting and loose lending standards which have since been tightened.

There may be scenarios where you can get into a place for 10% down but lending standards have tightened significantly in the last few weeks.