It's a good idea to run the numbers for them...because many times that simply compare your offer (say $50,000) to what the Realtor said they could get (say $80,000). Well, very few people actually get full list price, so let's say they buyer that comes through the Realtor offers $76,000. Well, a lot of buyers in that price range ask for closing cost assistance, which can be as high as 6%, or in this case around $4,000, which leaves you with $72,000. Plus you have to pay the standard seller closing costs (which I pay if I buy from you) which will run $2,000 or so for title insurance, etc...so now you're at $70,000. Then, after inspections, they find some outlets that don't work right, and some wood rot that has to be repaired, and it runs you a $2,000 to repair, and now you're at $68,000. And chances are, since you're listed at full retail, it will probably take 2-3 months to sell, and at your current mortgage payment of $800 per month, plus property taxes, maintenance, utilities, etc...you'll pay another $3,000 sitting here waiting for a buyer (hoping for a buyer), which brings you down to $65,000. And we haven't even gotten to the big real estate commission, which runs 6-7% in most towns, so there's another $5,000...bringing you to $60,000 (on our BIG $80,000 list price from Mr. Realtor). And that's just if everything goes JUST RIGHT. Here I am with $50,000 cash, close in a few days, and you're moving on with your life. It seems like it's worth a small price reduction to just be done with this mess, doesn't it?
That pitch isn't necessary for some sellers, who are desperate, and will give you a deal no matter what. But there are a bunch of sellers who are "motivated", and with a little help running the numbers will end up saying yes. It's that middle group that many wholesalers miss out on, because they're not willing to go the extra step to make it clear that their offer isn't nearly as low as it appears at first glance, when you compare apples to apples.
Best wishes to you!