Main sill (beam) needs to be removed and replaced though as it is carrying weight of the walls and home.But, it’s never just 1.  

@Amber C. the issue can be as simple as putting in some new footings with new beams, or it can even be jacking up the whole side of the house.

WE took down a 15x20 shed on cement block piers with steel I-beams across them.It surprised us that there was no cement between the blocks but 1" square steel posts inside each pier.The 'shed'  even had oak hardwood floors like those inside the1949 era home so we assume it was built then.. 

Glad I could help you narrow things down & put a laser focus the investment property that met your goals as well as risk tolerance Alonzo.

What you don't want to have happen is you get pulled into helping the brokerage grow when you are laser-focused on real estate investing.

Of course if they’ve been around for a while, you might be taking about trait and replacement beams, joists, etc etc... but it all depends.

A beam and carpenter to do the work usually runs me under $1000.

Back in the old days we used plywood between the I beams.

You kind of answered your own question in the same paragraph Austin, thats one way you could span that distance also could do a valeted ceiling or more headers or add a steal element, perhaps columns in the walls with beam. 

I have been getting quotes for work in a bathroom which includes some sheetrock, paint, flooring, and subfloor replacement (Pier and Beam house).