Supplemental floor supports in a crawl space, or basement, should always be properly installed, but often times a home inspector reveals that they are not.
These images in the video linked below are from a crawl space I recently inspected. The newer floor joists, do not appear to be properly fastened to the existing floor structure, as they are nailed rather than bolted. Also, the joist repairs do not fully span from the sill plate to the main support steel i-beam.
Also, the built-up block piers, as support supplements, do not appear to be properly installed. This existing floor structure appears to have dry rot in it, and also damage from wood destroying insects.
These present 'repairs' do not appear adequate, and should be further evaluated by a qualified professional. This is just one of many reasons that a quality home inspection is critical in order to be able to make an informed decision about buying a property.