Many kids and teens take on the responsibility of earning money long before they are eligible to be hired by a formal employer. Common miscellaneous jobs that could be included in this situation would be house-sitting, dog-walking, babysitting, snow-shoveling, and yard work or lawn mowing. This list is not all inclusive, but should give you a good representation of the types of jobs that are not taxable.
A key point is that these small jobs are not to be a regularly occurring steady means of earning income. The exceptions are lawn care/snow removal and babysitting. Babysitting is never a taxable service. Lawn care/ snow removal is only taxable after $5,000 in gross sales has been reached in a one year period. The $5,000 rule only applies to snow removal by mechanical means (snow blower/plow).