Why would he even do a 1031 exchange given that fact pattern?  What a waste.

It's not clear to me from the description of events that he *did* accomplish a 1031 exchange. I see lots of selling and buying and getting and putting, but no accommodator.

obviously, he did not do an exchange, but his LAWYER/EXCHANGE FACILITAOR says he did. Form 8824 line 18, just entering the items shown on Lacerte and also the form, do not seem to be complete.  what should I put on line 18?  Here is exactly what our Esteemed  Barrister wrote:   " sells property that has a 900,000 mortgage, but only a 500,000 basis on it for 1,000,000 and receiving 100K in net proceeds.  Then pays 100 K to buy replacement property for 100k, . 100 k of the capital gain from first property is deferred to 2nd property, the rest of the capital gain is taxed"     Then he continues " however if our guy used the  entire 100 K for the down payment on a 500,000 property, and financed the remaining 400K of the purchase price, then the entire capital gain is deferred onto the new property, (which will then have a cost basis of zero)"

As stated, there really is no purpose to trying to generate the 8824. A straight sale and purchase of the new property would have generated the same $500,000 gain. 

Use Ctrl + W to see the batch input for screen 17 and it should look something like my image. I think you did not input the $900,000 for Old loans on property given up  (code 18)