If I can get away with sealing it for 1-3 years for $1000, do I go ahead and delay the new roof (which will cost at least $7k if I go with a licensed roofer, $5.5-6k with an unlicensed)?  

Lots of these marketeers are not real buyers but simply working as unlicensed brokers.

It should be noted, however, that claims for equivalency by unlicensed persons for activities which require a real estate license will not be considered.

All contracts, options, or other devices not based upon a substantial consideration, or that are otherwise employed to permit an unlicensed person to sell, lease, or let real estate, the beneficial title to which has not, in good faith, passed to such party for a substantial consideration, are hereby declared void and ineffective in all cases, suits, or proceedings had or taken under this chapter; however, this section shall not apply to irrevocable gifts, to unconditional contracts to purchase, or to options based upon a substantial consideration actually paid and not subject to any agreements to return or right of return reserved.History.

This is the problem that stops most unlicensed brokers from operating honestly, ethically, and from victimizing sellers.

This has been expressly addressed in the statutes to put an end to unlicensed brokering.

Then today I read some negative posts here that were rather derogatory about wholesaling, referring to wholesalers as unlicensed brokers and some other negative connotations.

If the owner is ok with working with an unlicensed middleman for selling their non performing commercial asset you then have to evaluate the value of the property if your going to make any kind of offer.

Basically they are just acting in the capacity of a dishonest unlicensed Real Estate agent.  

However I think if you use that formula and deduct those few items from your ARV  you will be in the ball park.Although  Make sure you don't run afoul of the licensing laws .. you may want to look at The BRE website right on the front page has a item about unlicensed activities.. so make sure you know what your doing here..