A common rule of thumb in Business Angel investing is that approximately half of your investments will return little or nothing, 30-40 % will give you your money back (perhaps with a small profit, often just covering the “interest” for the time it took) and approximately one in ten will give you a real gain. One case should in other words compensate for the half that became nothing and give the upside for the whole investing activity, meaning a return of ten times the investment or more.
It is advisable that private investors seek expert advice to understand the outcome both financially and in the tax perspective.