Many people want to start growing a marijuana garden but don't have a lot of money to buy all the equipment. Here's a list of the most important items and what I would recommend. It is possible to set up a cheap indoor marijuana garden grow room. Marijuana plants need light, water and co2. Also, the temperature should not be too low or too high and a little fertilizer is needed. Light - The most important and also most expensive item to buy, for your indoor marijuan garden, is the light. You should buy a 600-watt High Pressure Sodium (HPS) light. It will cost you around $30,- but it will pay for itself after one harvest. Experienced marijuana grower yield up to 21 oz of marijuana with one HPS 600-watt light. Of course all the other circumstances should also be perfect but still, an inexperienced grower with a cheap set up can yield 4 to 8 oz with one HPS 600 in 3 months. You can use fluorescent lights but the yield will be less. You can get an LED grow light, which obviously costs more money up front, but saves you a lot of money in the long run with savings from lower electricity bills. Plus there is the frugal bonus of having a cooler room, which saves money on fans and AC. Water - Just use regular tap water for your marijuana garden. If you can drink it so can your marijuana plants. Professional growers use corrected water with pH between 5.5 and 6.5 and EC between 1.8 and 2.2. There are 3 common methods for testing these values, but it will also work fine with regular tap water. Use some nitrogen (N) during the growth phase and some N-P-K during flowering. Co2 - All green plants, marijuana included, use light energy, water and carbon dioxide (Co2) to produce energy in the form of sugar for its growth (photosynthesis). You can use a Co2 tank with a regulator but you can also install a simple ventilation system to refresh the air in your marijuana garden grow room. Place a fan in front of the air-inlet and create an opening (as high as possible, hot air rises) where the warm air can escape. Climate - The temperature should not drop below 64 and not get higher than 86. Around 77 is perfect! The HPS light will produce a lot of heat so if you install it in a 1x1x2m closet without ventilation temperatures will rise up to 125. Use a little more space and temperatures will be fine. All plants should move a little by the air flow in your grow room, just like the wind normally makes plants move. Tips - Use aluminum foil instead of mylar or other reflective foil. Buy used equipment and be creative. See how you can set up a simple homemade hydroponics system. You don't need a water pump, a bucket or watering can will also do. Also, you'll need to read a lot about growing marijuana, Seeds - Of course you need some high quality marijuana seeds!