I recently started trading penny stocks with the advice of a friend. He told me to buy a certain stock at $.0001 and told me to hold on to it until it doubled. I bought $150 worth of that stock. I waited about ten days without seeing any results. The price would jump to $0.0002 buy my sell order wouldn't execute. My friend told me to be patient and said something about a market maker buying it at $0.0002. After ten days the price of the stock tripled at my sell order filled at $0.0002. I walked out with $150 in profit (doubling my money.) My friend on the other hand doubled 4 thousand and ended up with 8 thousand dollars.

Now I am tempted to invest $1,000. My question is doesn't this seem too good to be true? My friend claims that there is practically no risk involved because you can always sell back your stocks at $0.001 to the market maker who would buy it immediately. Is this true? What else should I know before buying any further? THANKS!
Additional Details
CORRECT ION TO LAST PARAGRAPH: My friend claims that there is practically no risk involved because you can always sell back your stocks at $0.0001 to the market maker who would buy it immediately. Is this true? What else should I know before buying any further? THANKS!