Ichabod Crane has two jobs.  His main profession is that of schoolmaster in the Sleepy Hollow schoolhouse.  He is a strict teacher who is not afraid to use a birch on the unruly if he deems it necessary, but he is also encouraging to his students.  However, Ichabod makes very little money as a schoolmaster.  This is a problem for him, as he has a large appetite for delicious food and desires to have more money.  To subsidize his meager earnings as a schoolmaster, Ichabod Crane has a second job teaching singing lessons.  He takes great pride in his singing voice, and is eager to display it at church each week.  He teaches psalmody to local young people, for which he is paid in shillings.

What is Ichabod Crane's job in "The Legend of Sleepy Hollow"?

Ichabod Crane is a schoolteacher in the town of Sleepy Hollow.  Here is the quote stating this:

• Ichabod Crane, who sojourned, or, as he expressed it, "tarried," in Sleepy Hollow, for the purpose of instructing the children of the vicinity.

He is not the most fair or proper schoolmaster, however.  He disciplines his children not based on their offenses, but based on their stature.  The same offense may be committed by a weak and a strong child, but the strong child will get the harshest punishment:

• on the contrary, he administered justice with discrimination rather than severity; taking the burden off the backs of the weak, and laying it on those of the strong. Your mere puny stripling, that winced at the least flourish of the rod, was passed by with indulgence; but the claims of justice were satisfied by inflicting a double portion on some little tough wrong-headed, broad-skirted Dutch urchin, who sulked and swelled and grew dogged and sullen beneath the birch.

He was fond of walking his young students home.  Not for their own safety, however, but in hopes of getting some good food from their mothers or in hopes of spending time with good-looking older sisters.

• and on holiday afternoons would convoy some of the smaller ones home, who happened to have pretty sisters, or good housewives for mothers

In the short story by Washington Irving, Ichabod Crane is a very strict school teacher and a music instructor. This is very different from the character in Tim Burton's film Sleep Hollow, in which Johnny Depp plays Detective Ichabod Crane. 

Your question is a good example why it is always important to read the story and not depend on watching the movie. Besides, the real writing is usually better than film adaptations, in my opinion. 

There are a number of other differences between the Depp film and the short story "The Legend of Sleepy Hollow."  For more information about the story and characters, see the link below: