Seven is a bit young for the businesses that you mention; they require too much monitoring on your part. We expected DS to do regular chores, such as making his bed, picking up his toys, clearing the table, plus personal hygiene. To help the monitoring & remembering, he had a sticker checklist. He could earn money by doing jobs beyond this like emptying all the trash & recycling cans in the house, sweeping the garage, or raking leaves.
Twelve is the age where more businesslike jobs could be considered. Babysitting, if trained. The Boy Scouts have an Entrepreneurship merit badge that requires starting & running a business for 6 months. DS decided to plant, harvest, & sell home grown tomatoes -- he netted $400 profit. Another scout did walk dogs.