In order to inspect the property, the lady recommended me to introduce myself to occupants as "from building department" or use some creative/salesman tricks.

I know they can be difficult, so are there any tips or tricks to increase the odds at all?

The trick is for them to sell it prior to sale.

So, IMO, the trick is identifying the opportunities that exist and then finding ways to fit such into your plan, Not all opportunities fit, you can't force a deal, it has to flow into your operations.Doug is right that you may not get deep discounts walking into a bank.

A padlock would do the trick.

Should do the trick.

Or does anyone know of any other tricks? 

Kind of a cool little trick.

You don't have to go for a stucco look, just a light knockdown will do the trick.

It will be the trick of finding a balance between giving him something worth while vs giving up more than I possibly want to.Though...