What is the best and most cost effective way to add support to and lift up the main support beam?

On the other hand, bigger buildings tend to be built on caissons with "grade beams" - so that the building itself sits directly on bedrock. 

My point exactly, if you can't have a little fun why bother.This business is often stressful, tenants can be a major pain in the butt.When your stuck with a nut job let lose the squirrels.Think of crazy tenants like a kitten......and the landlord has the laser pointer.

When the mason removes the old stucco he finds a wooden beams spanning the width of the property that is severely compromised with rot.

If I put one on the floor, I place it upside down because  One of the beams angles downward in normal position.

Open concept being all the rage these days, Ive seen bearing walls removed without installing a header or beam to carry load.

The contractor found a beam that would need replacing and a few other minor things, so I went back and told the wholesaler I could only do $80k.

A Client bought a MF property through an acquaintance of theirs, it had an on-site "manager", and 15 units according to the paperwork I was provided initially. 2 of the "apartments" were under one of the houses (post and beam construction, all open).

I seek a mentor that is driven, focused, successful, and wants to share his/her knowledge with a very motivated and laser focused young entrepreneur.

The truss system is in good shape and can be saved, the framing lumber and several large laminated beams can also be salvaged if the house was deconstructed.