Before you get ahead of yourself, you'll need some more groundwork. The fact that it's in a Land Trust suggests investors are already involved. You need to sort out the title issue before you proceed. Tell your seller you'll probably be able to buy it, but you need a few more details, and need to see the Trust, or at least find out who the Trustee is. The latest Deed will be in the courthouse, and its image may be on your county's website. Once you find the Trustee, that's who you'll be dealing with. If it's dead Grandpa, you'll need to see the Trust doc to find out how the successor Trustee is chosen.
S/he may be designated by the beneficiaries to the Trust.
You'll also need to find a title company that can do an "O & E" report (Ownership & Encumbrance) or whatever a basic title report is called in Illinois. It may cost $100 or so. Make sure there is only one mortgage, and that there aren't other liens that may have to be paid off. If there are, now you know, and can proceed accordingly.
Unless you know an investor you absolutely trust not to try to "steal" your deal--or feel like your luck is good--you may wish to get at Purchase Agreement spelling out the price ("balance of mortgage") and terms, ("subject to existing mortgage") but make sure to give the Trustee at least $10 as earnest to bind the deal.
Once you have that, you can file an "Affidavit Regarding Real Estate" at the courthouse announcing to the world that you have a deal pending. This will cloud the title and block anyone else from buying it. Don't do this until you're sure you plan to proceed, and you may need a good RE atty. or fellow investor to accomplish this.
You may be able to buy it by being appointed as the Successor Trustee, or by becoming a/the beneficiary using a document called "Assignment of Beneficial Interest of a Land Trust."
This deal sounds like gold, though, all the more so if you can buy it sub2 AND be able to offer it sub2 to another investor. A savvy investor will recognize the value of paying,say, $50k for the right to take over $93k of payments on a $300k property. Once you're on title, you could also just try to retail it, get a Realtor, choose a good sell-it-fast price, and away you go!
This isn't a precise road map--I've done sub2s but don't use Trusts myself--but it should help to point you in the right direction. If it sounds difficult, well, consider if it was easy someone else would have plucked this rose of a deal already. Good luck!