Lots of people want to grow their businesses or jump into a market and sometimes the easiest way to do this is to buy existing businesses. Remember that the largest generational demographic in the US is hitting retirement age. There are a ton of businesses with no exit plan waiting for you to buy them and given the tremendously low interest rates that exist the best way to buy them just may be through leveraging debt in the purchase.
You can secure debt through loans to purchase the business. This can be done through third parties such as banks and through professional investment companies. In purchasing a mature business the financing companies aren't interested in speculative upside (like investors) they are interested in cash flow and the ability to repay the debt and service the interest.
If loans through third parties aren't the route to go then consider purchasing the company and paying the former owner as a loan to him that is paid out from the cash flows of the business. In this case you'll probably need to put up an amount of money out of your pockets, say 20 to 40 percent. You'll take over the company and pay to the former owner payments every year out of the business cash flows. You may be skeptical of this idea.
Why would someone want to get paid out of a profitable business? Why not just keep it? In most of these situations the business doesn't exist without the owner involved. If the owner had an accident then the busienss would shut down. This makes it very difficult to value a business as a traditional valuation and purchase and it adds to the overall risk. If you are willing to take over as the owner/manager then you have the advantage over other buyers. You may have the added advantage as being the person to keep the company in tact. Other buyers might just tear it apart on purchase. The former owner gets to get out from under the business and gets a stream of passive income. That is quite a plus for them.
You can also cash in your assets and purchase a company. I have a friend who mortgaged his house to buy an existing business. This was as simple as securing a mortgage. With mortgage rates as low as 3.5% it would certainly be the lowest rate out there compared to standard business loans.
What is important is to have a realistic plan for paying off the debt and making sure the equity you build up can be made available to you. For example you can get revolving lines of credit once you've been retiring your structure purchase debt. Also make sure you don't become the owner/manager trapped under the same business you just bought.