Growing indoors stealthily can easily be done for cheap. It doesn't matter what is being grown; for everything from plants to tomatoes or herbs, the setup is the same. The easiest way to create a stealth growing environment is by converting an old refrigerator into the growing environment. Costs will vary depending on the quality and brand of some of the components used, but the entire setup should cost less than $100.
Find a refrigerator. A refrigerator is the ideal space for a stealth indoor growing environment; it is secure and provides ample space, and it is not obvious there is a garden inside. The best refrigerators are ones without a freezer, and those that contain no drawers or ice makers. Ideally, it will be a hollowed out rectangle. Such a refrigerator can easily be found for cheap or free (since it doesn't need to work) at a garage sale, or through a classified listing.
Prepare the growing environment. Strip out the contents of the refrigerator, take out all shelves, ice makers and drawers. Remove the exhaust fans. Each refrigerator comes with two exhaust fans. Removing them is easy; they are located at the back of the refrigerator and can be removed by removing the screws with a screw driver. Pull out the exhaust fans and any related parts such as tubing or motors. Line the walls of the grow environment with Mylar or aluminum foil to reflect the light; this is good for the plants.
Install the lights. For this type of growing environment, use fluorescent lights. While they are not the most powerful or ideal for growing plants, they also are inexpensive and produce little heat. Measure the space in the refrigerator and purchase fluorescent lights and fixtures that fit the length of the refrigerator. Purchase enough lights to cover the entire area of the refrigerator (length X width = area). Fasten the lights to the interior roof of the refrigerator so the light shines down below. Insert one of the racks that originally came with the refrigerator into the highest slot for it and use twist ties to fasten the light fixtures to the rack. Alternatively, drill the light fixtures into the roof using a handheld drill and screws, if a rack is not available. Take the power cords of the lights and tie them together on top of the refrigerator rack. Insert the plugs into a power bar and position that on top of the rack as well. There should only be a few inches above the rack (since it is mounted in the highest position), this area is ideal for storing excess power cables. Pull out the power cord cable through one of the exhaust fan ports so it can be plugged in. Plug the power cord into a timer; this will regulate when the lights turn on and off. A timer can be purchased at any hardware store for less than $5.
Purchase 2-3 exhaust fans, the number purchased will be related to the number of fans removed earlier.
Bathroom exhaust fans are ideal because they are cheap and effective. Mount the fans on the exhaust outlets of the refrigerator, point one facing in, and one facing out. This ensures a flow of air through the growing environment. Fasten the exhaust fans to the refrigerator using a drill and screws. Duct-tape the edges of the fan to the refrigerator to ensure a good seal, this is not necessary but helps.
Connect the power. Plug in the exhaust fans and light power cables. Test to make sure everything works. Setup the timer as per ideal light and dark settings for the garden. The fans should always be on.
Set up the freezer (if applicable). If the refrigerator came with a freezer, it can be used to store growing supplies, or it can be converted into a nursery for cuttings. Use the same installation process for the main grow environment for the freezer. The freezer requires no exhaust fan, but it does require a hole for fresh air to flow in and out. This can be made by removing the freezer's exhaust fan. Also, for a nursery, not as many lights will be needed.