Selling with a 1031, Can I seller carry back a 2nd Mortgage

[Bob E.]

We have on an offer for 20k over ask on our Phoenix listing (on the market one day) and the buyer is worried about the appraisal.  

We are selling through a 1031.  Can I offer to carry back part of the sale price if the appraisal comes in low?  I could find a friend to write the second and then buy it back from them after closing but it seems simpler if I can write it myself.  I do have cash if I have "fund" the sale" and take the note back.  TIA