You can invest in real estate crowdfunding platforms for as little as $1000 or invest a few thousand dollars in REITs or alternatively you would need a 20 percent down payment to purchase a real estate property which could be around 200k for a million dollar home. In the end, the amount of investment depends upon the location and type of property. 

Crowdfunding Sites: Sites like fundrise allow you to start with as little as $500 to $1000 when investing on their platform. There are many crowdsourcing sites out there and you need your due diligence before you invest. Try to find out your priority as a lender in case there is a loss in the investment you make. You do not want to be at the bottom of the lenders list in this situation. 

REITs: If you want to invest in Real estate income trusts, you can probably invest like you invest in shares in the stock market. You can make an investment of a few hundred dollars but many beginner investors purchase upwards of $10000 worth of shares in a REIT. 

Down Payment: Investing in single family real estate is probably the most common and safer ways of investing in real estate. Most of the purchase would be covered by your mortgage company as long as your income is verifiable and good and you have a decent credit score. What you would require is the amount required to cover your down payment which could vary depending upon your property type and scale. Typically mortgage companies ask for a 20 percent down payment which could be $40k for a 200k property or $200k for a million dollar property. The down payment amount varies and is different for each individual depending upon the cost of the property. Some countries like Canada allow first time home buyers to purchase a property with as little as 5 percent down whereas self employed people may have to arrange 35 percent down payment. 

Partnership: Another common way of investing in real estate is through partnership and a few investors go this route. They require capital of 20 percent down payment plus renovation costs whereas the remaining capital is invested by private or b lending companies. You need to be extra careful while dealing with private lenders because these lenders charge a high fee in addition to the mortgage payment to setup the mortgage. It is not uncommon for partner investors to start with a total capital of 400-500k to buy a million dollar property and then renovate it to sell it for a profit.

So the amount of money you require for real estate investment completely depends upon the investment route you take and can vary for each individual.