You will in effect be managing the property for whatever the cash flow is if you have to give it back in five years. 

Net effect will be the same,  but you're freeing up a Fannie Mae "number of financed properties" slot every 7-8 years instead of every 20 years. 

What other types of marketing are effective for wholesalers?

It's simple, but incredibly effective.

I did take over someone's contract last year on deal, but usually it is more cost effective for me to pay more on marketing myself than buying from wholesalers. 

Perhaps there are more effective ways to "offset" capital gains, but this has been my experience.  

Do you have any tips on setting this up effectively without breaking the bank on legal and other filing fees?

It looks like you may have kids, so I'd also take time to consider how your decision may effect you, your kids, and what may be left of your relationship with your ex.

You might check if there is a municipal occupancy code in effect.

If I were you, short of sitting behind a bush for 24 hours to find the culprit, I might have a sign made to post by the dumpster that says something to the effect; “Dumpster under 24 hour Surveillance -no unauthorized dumping allowed”.