In commercial landlord / tenant law, the law follows the lease.  This means that businesses should be knowledgeable about the contracts they sign.  Businesses should intend for every sentence to be there.  Illinois is no different from most states, in that it upholds freedom of contract, as guaranteed by the 14th Amendment.

For residential leases, the law presumes that average residents want a livable place.  The law also presumes that average residents may not be experts in drawing contracts or in landlord / tenant law.  That is why private residents often have recourse over landlords who demand eviction in unfair circumstances. 

Landlord rights are almost endless in commercial renting law.  If a commercial tenant attempts to sell the business, the landlord may be able to recapture the lease.  Late charges and security deposit may be excessive.  There are no privacy rights or right to quiet enjoyment of the property. 

By the same token, Illinois state law upholds the freedom of businesses to create their own rights.  Businesses can contract for ?restrictive covenants? to limit the kind of businesses that can occupy adjoining spaces.  For example, an Illinois shoe store can restrict the landlord from renting out the next space to another shoe store.  These covenants help promote fair competition. 

In business agreements in general, the Illinois law gives merchants, who are experts in their own field, the freedom and leverage to make a good deal for themselves.  The law does not pretend to know more than a businessperson what a good deal is for that businessperson.