You can advertise your parking offer locally in the classified ads of local newspapers, or go to websites like Remember to include important information in your advertisement, including distance from local transport links and anything that will set your place out from the crowd, such as having 24-hour access or the fact the garage is in a CCTV area. You can charge up to £50 a week depending on where your parking space/garage is and how secure it is.
For example, your business receives a $1,200 pre-paid credit card from a supplier in consideration for business dealings or as a token of loyalty. This amount is taxable and you must report it as income for your business. If your business is incorporated, and a shareholder uses the pre-paid credit card personally, the shareholder must also report the amount as income. 
I have a lot more than seven streams now. But I think just a few is fine. Especially if they are high-quality and don’t take much time. There was a time in my life when I only had three income streams, but I could have easily lived off just the passive income streams. The key is having at least a few. If a doctor has only 1 income stream, they could be hurting even with a high income. A dozen is likely too many for most since they don’t have the time to manage it properly. 3-5 would be great for most doctors – especially if you are a lumper and not a splitter.
Philadelphia (earned and passive income; income must be reported to the City of Philadelphia if Philadelphia tax is not withheld by employer; residents must file the Earnings tax form to report wages on which Philadelphia income tax is not withheld, the Net Profits tax form to report self-employment, business, and most rental income, and the School Income tax to report passive income excluding interest earned from checking and savings accounts; an additional Business Income and Receipts Tax is also imposed on business income sourced from Philadelphia; individuals earning less than amount that would qualify them for the Pennsylvania income tax forgiveness program are eligible to receive a partial refund of their wage tax withheld by filing a refund application)
This venture requires both time and money, but it is certainly worth it. Making low-risk investments with your savings offers higher dividends than letting the money in the bank. While buying stocks in large corporations comes with a high degree of risk, mutual funds are relatively safer and less volatile. They also offer higher return-on-investment compared to fixed or recurring deposits made in banks.
When you build a business, you're giving up active income (instead of working for pay, I'm volunteering at my own business) for future active and passive income. In the meanwhile, you'll need a way to pay for your expenses. It could be that you're building a business on the side, so you still have a day job, or you're living on those savings. Either way, you need a cushion.