@Tyler Hall
Bring out a few contractors to bid the property, then provide the list of the contractors and their bids to an investor that buys the property from you. So they give you an estimate, and the investor gets the names in order of bids, thus you are just referring them (potentially getting them a job, once again acting as the middle man). When you are wholesaling, you could be selling the contract to someone across the country too. Having a list of contractors and bid amounts to provide to potential investors could actually make the deals more appealing to them as they will be able to run their numbers very accurately, and they know they have someone willing to do the work on the place they are about to put their money. So in summary to your question, chances are if they give you a good bid, you are going to send them as the go-to contractor to your investor getting them a job, just as if you would've shopped bids to buy the property yourself.
Also, I touched on this in my first post, but trying to build a successful wholesaling business is just like any other business. If you screw over an investor with a wildly inaccurate guess as to what the market is charging for a rehab, you are burning a partner and who knows how many more future deals. Opposite to if you establish yourself as a business that is always right with the numbers, as well as going the extra mile of having leads for contractors to hand over to your partners. They tell all of their investor friends, and BOOM, you now have 3,4,5 more investors on your "buyers list" to send new deals to.