If you're interested in online marketing, setup email software and create a lead magnet that you can use in your sales funnel. Then, build up that list. It's often said that you can expect to earn about $1 per subscriber per month. If you have a list of 10,000 subscribers, that means you can earn roughly around $10,000 per month. You will need to deliver value and not pitch them on every email, but it is a very achievable goal in a short period.
Complete errands or tasks for the elderly. Older people often need help with buying groceries, cleaning their home, performing home maintenance, and paying bills. To find clients, contact your local community center or church to find out if anyone needs help. Additionally, you might post an ad in your local classifieds or talk to people you know to find out if they know someone who needs help.