IANAL, but it seem to me that each payment would be taxed as ordinary income, provided that the received asset is liquid and there is a well-functioning exchange to determine its fair-market value (in USD).  The IRS FAQ (https://www.irs.gov/pub/irs-drop/n-14-21.pdf) mentions that it might also be subject to self-employment tax if carried on as a business as opposed to a hobby.