It's interesting because it's usually the people 65 and over who will cash winning tickets over $600, but under $2000 for 10%. For a $5000 ticket, they will charge 25% because there is a possibility they will have to pay taxes on a percentage of the winnings.
Since you have IRS problems you're paying or should be paying Federal taxes on a percentage of your income. You probably paid at least 10% in Federal taxes last year so an additional $5000 in income might raise your tax percentage and even if it didn't, it will still cost you $500 more in taxes. This "favor" you're doing will cost you at least $250 out of your pocket. He can't find anyone who will cash his ticket for less than a $1000 and most would ask for $2500 after hearing the circumstances. It's a terrible deal.
"so you think i will have problems at lottery headquarters?"
Possibly because you live in Illinois.
"If you won $600 or less, collect directly from the closest Lottery retailer. If you won more (niiiice), you are required to fill out a claim form. Just file the form with any retailer or mail it to the Illinois Lottery and you'll get your moolah in 4-6 weeks. To be on the safe side, we recommend that big winners mail forms via guaranteed mail.
Reminder! When you visit a Prize Center to file a claim, make sure to bring a photo ID and some means of verifying your Social Security Number. Thanks."
"then i have to cash this check and give him a money tomorrow"
In other states like Michigan, Ohio, and Kentucky winning tickets over $600 and $5000 and under can be cashed and paid the same day without going through lottery headquarters avoiding any checking for back taxes though in Ohio you're asked about back child support. Because you said "cash this check today and give him the money tomorrow" it looks like Illinois has a similar method of collecting the winnings on the same day.
When you sign the Illinois claims form, you're signing under the penalty of perjury "that no other person is entitled to any part of these payments". Is doing a favor that will probably cost you money worth possibly being changed with defrauding the State of Illinois and paying a maximum fine of $10,000 and/or up to 3 years in prison?