Establish a relationship with a lab
For lab/pathology work, many DPC docs negotiate prices (often low or wholesale ones) with national laboratories (Cedar, CPL, LabCorp, Life Line, Quest, etc). The lab then bills the DPC practice (not the patient) for their services. Some docs treat these labs as a benefit of membership and swallow the cost; others pass the cost through to the patient (potentially with a small markup). This can save your patients a lot of money.
Offering this service to your patients requires negotiating prices with labs upfront. In these discussions, demand similar prices to those already established by previous DPC docs. Check out the price sheet AtlasMD negotiated with Quest.
There may be legal hurdles to doing this depending on your state. For non-pathology lab services, it is illegal in New York and New Jersey (see here). For pathology services, it is illegal in many more states; see the "direct billing" states listed here.
In these states, the patient must arrange payment directly with the lab. Contact the lab to determine the best way to go about this.
Establish a relationship with an imaging center
As with labs, it is possible to negotiate low prices with imaging centers. Reference AtlasMD's imaging price sheet.
Establish relationships with other providers
Consider arranging prices for bariatric surgery, breast health services, digestive disease specialists, endoscopies, eye surgery, general surgery, heart and vascular specialists, kidney stone treatment, oncology specialists, orthopedic surgery, pain management, physical therapy, radiology services, sleep health centers, and spine procedures.
For your reference, price sheets for each of these categories can be found here.