There a couple of websites - these websites touting nationally licensed inspectors seem to have proliferated recently so you still have to be careful.
I'd look at all three and see which has been around the longest and then look for an inspector that has been around for awhile and has experience or accrdition from a previous related career field like plumbing or carpentry.
Then ask for references?

http://www.nachi.org/

http://www.nahi.org/

http://www.ashi.org/

Illinois requires HI's to be licensed.

That said, be aware that the professional organizations listed above will list a home inspectors even if they have no license to practice in the state in which they are listed...which says quite a bit about how much the organizations judgment can be trustedÂ.so best bet, donÂt even waste your time on their websites.

That said; ask for referrals from family...friends...and your attorney. Once you obtain the namesÂÂcheck to see if they are licensed and if they have had any disciplinary actions against them..

From there on focus on the type of inspection.......and not the cost.
Do not fall for the "same day check list report'...as it serves the HI ...and not the buyer. Such reports are the least informative...with only the very basic info...and generally result from a speed focused inspection, as opposed to a thorough inspection.

Choose an HI who provides full narrative reports...not boiler plate...with digital photos...who carries errors & omissions insurance, which is not required in your state...but responsible home inspectors carry it in case they do miss something...this insurance provides the buyer with recourse....and...check references.

An average house of average size should take at minimum 2 1/2 hours to inspect...anything less...and you are not getting what you deserve.

Last but not least, you get what you pay for...so, as enticing as the low ball price may be...when you consider the money you will have on the line with buying a home, the penny wise pound foolish adage will most likely come back to bite in the end.

Here is a link that might be useful: Illinois Licensee Look Up

BTW, Indiana requires licensing as well..and general liability insurance...but not errors and omission. The above advice on the E&O sttll stands.

Here is a link that might be useful: Indiana Professional Licensing Website

Ask friends and family. I was lucky and found my inspector thanks to a referral from a friend who was also doing the home buying thing at the same time as me.

People often say to ask for referrals but I've had bad ones from well-meaning people who were uh.....not fussy. So get referrals but back them up with your own research.