Newbie selecting between contractors

[Jamil Barton]

I purchased my first property in December, a 3-unit property - one duplex and a carriage house on the same low. The inspection suggested waterproofing in the carriage house, and 1-2 pilasters/I-beams in the duplex. 

After closing, I've head different contractors come in and give me very different assessments of what is needed. 

Contractor A recommends:

• Carriage House: Waterproofing and no pilasters/I-beams
• Duplex: 2 pilasters/I-beams
• Total Price: 11K
• Note:Despite bowing along the BACK walls in the carriage house, his assessment is that this happened a while ago and I probably don't have to worry more about it. He seemed the overlook the observations of contractors B and C.

Contractor B recommends:

• Carriage House: Waterproofing and two pilasters/I-beams along the LEFT wall.
• Duplex: 5 pilasters/I-beams along one wall.
• Total Price: 45K
• Note: This contractor is prohibitively expensive, but was very detailed and felt more professional than contractor A. 

Contractor C recommends:

• Carriage House: Waterproofing and 13 pilasters (5 on the BACK wall, 4 on the LEFT wall and 4 on the FRONT wall)
• Duplex: 5 pilasters/I-beams and a buttress wall.
• Total Price: 23K
• Note: Contractors C and B shared several of the same observations overlooked by A. And, somehow, contractor C is about half the price of Contractor B, despite recommending more work.

Because this is my first property, and I have not worked with contractors before, I'm at a bit of a loss. Looking at the walls, they are arriving at very different conclusions of how much work needs to be done to ensure no further movement in the basement walls against the soil pressure. I also can't tell if Contractors B and C are just trying to sell as much work as possible, or if Contractor A really overlooked needed work.

My best guess for approaching this is hiring a structural engineer to give me an assessment, on the assumption that they would not have a monetary incentive to try and upsell the work. I could also have more contractors come out, but with a full time job - time is short, and I have some other issues to tackle to make the place tenant ready. Recommendations welcomed.

Thank you!