Upload & Sell: On
Treat them as real estate photographs ... sitting fee, & costs to produce prints up front. Additional profit @ due closing ... CONTRACTUALLY WRITTEN.
Don't buy into the "blog thing" ... if they legitimately have the contract to list & sell the property ... and are building a "special site" to market from, they still have advertising / marketing capital to work from.
Write your own contract (rough draft to start) as to what you want / need from it. Then consider that they are simply trying to minimize their upfront capital outlay (which does NOT MEAN THEY HAVE NONE AVAILABLE). Cover your bases at your costs & time ... offer to take MOST OF YOUR PROFITS on the back end @ closing, but have it be LEGALLY BINDING that you get yours then ... and make it worth your while. Consider where your risks are ... safeguard them. Consider where THEIR risks are ... safeguard them (notice yours came first). They are "waiting" for the big "payday" at closing. Be part of their team and wait on your "payday" at closing as well ... but don't wait on your expenses (up front).
When I do real estate pics ... I do them to "HELP" THE SELLER MOVE THE PROPERTY (as part of the marketing team) ... but I get some of mine up front, and even more on the back end for the higher valued property. My real estate agents keep ringing my phone because they appreciate I'm sharing the risk with them ... not gouging them ... but also covering my bases and waiting on the bigger payday at the back end.
Them asking is a good thing & proper. But, this is not an "oh gee, this sounds like fun, good exposure". If they come ask me to shoot them ... it's going to cost them ... but I'm flexible in structure, but I'm also not going to get "hosed" in the process. If I'm helping you make big $$$ by doing a part of your job that you can't (superior marketing materials) ... I get a piece of the pie as well. If you (real estate agent/broker/seller) can't appreciate that ... good luck with your point & shoot and on camera flash.
BTW ... pics don't sell property ... they help get the agents phone to ring and put a memory into people's minds when shopping @ preliminary stage that hopefully makes them want to see more ... "Ring, ring. Mr. agent, can I see ... "
IMO ... don't give it away or take on the risk that could "die on the vine". But if they'll joint venture the expenses up front ... then reciprocate the joint venture @ profit on the back.
I figure if I'm doing 5% - 10 % of their job for them (marketing materials) ... I should get 5%-10% of their commission @ closing (even if I discount to 3%-5%, it can still be a nice number) ... or they can just pay for it upfront via a day rate or retail flat fee and I go on my way.
Risk / Reward ... it cuts both ways.
If they are willing to SHARE the reward with you, you might consider SHARING the risk with them ... otherwise, "NO FREEBIES".
Don't play the game of you put up the risk, they reap the reward ... feigning some promise of "snake oil" reward for you @ exposure. They are in it for the business of money ... so are you. That doesn't mean you have to be "tough guy" @ hard line ... but, if there isn't any "hard" money in it for you (not the promise or hope of "potential" or "credit" or "exposure") ... either now or later ... PASS.