Without a doubt the biggest cost of an indoor grow is electricity. I sure would like a giant grow room with a field out back to put all our solar panels there. That would be the way to do it. Unfortunately if I had a gazillion dollars for all that stuff I wouldn't be so worried about growing on a budget.
The price of the sun is in my budget. If you have a way to get your plants in the sun that would be the ticket. By putting your plants in pots that makes them able to be moved but you still have the time of year on the central coast to deal with. If it's the winter the day is short, in the summer it is long. You have to work with what you have. If your plants are in veg and it's summertime than everything is honkie dorie but what if its winter? You have to work your lights to go with the plant. If your plant is vegging in the fall or winter you can either move them inside to extend the light hours or move a light outside on your plants. Right now as this is being written it is October in San Luis Obispo County. I have my vegging plants outside on a friends property. I also have lights that come on at the end of the day for a couple of hours and then back on just before sunrise for a couple hours. This makes sure the plants don't get 12 hours of darkness that they needs to flower. My plants are perfectly happy in veg and I only spend the electricity for 4 hours of light per day. That's what I call having my cake and eating it too. On the other side of the coin it could be July, the middle of summer and you have some beautiful plants you want to flower. Now they need light deprived. You can either move them back or forth inside where it can be dark for the 12 hours of darkness they need every day or you can build a frame. Cheap with PVC pipe and black plastic. Now everyday at the alloted time you can simply put your black plastic framework over the tops of your plants and now it's night. The frame is light and very easy to move. You do need to take the time to move it everyday and at the same time. I know it's a pain but it will fit into about any budget. The sun will always remain the cheapest light you can use. Between black plastic and a supplemental light you can keep many more plants growing throughout the year.
Indoor growing does require lights and a much heavier dose of electricity. There are many options for lights. Some are expensive up front and some are cheap. One thing though I think when I have bought a cheap light then PGE always hands their hands in my wallet. LED lights have a very low power consumption but WOW do they hit your wallet up front. LED's can get in your pocket book for over a thousand dollars up front. Not always but the best ones are. The best deals that I've found can be at any hardware store and thats CFL's. They are very impractical for a commercial grow but for a few plants at your house they will do the trick. Compact fluorescent lights are the little curly Q light bulbs that I'm sure you have seen many times. Cheap to buy and doesn't require a special fixture. You can put them in a little lamp that you can buy at a garage sale or thrift store for a couple bucks. Easy as screwing in any normal light bulb. No ballasts, no special reflectors, and no big electric bill. They also have the added benefit of very low heat. Your plants can practically touch them. You do have to remember to get the right Kelvin rating though. This is the temperature of the light coming off your bulb. Look for about 6500 degree bulbs to do your normal vegging of your favorite weed. When it comes time to flower you should be looking around for a temperature more in the 3500 degree range. That way these bulbs can more closely duplicate the respective seasons and the color of the natural sunlight at that time of year. In fall and winter the sun has a softer glow with a higher amount of red sunlight comming off the sun and in the spring and summer the sun has a stronger white light almost even a blue color. If you plug these bulbs in side by side you will easily see exactly what I'm talking about.
So lots of options here. I still think that when ever possible if you are on a budget the sun is the number 1 option. Cheap and stronger than any light I've ever seen at any grow shop. Just remember that when it's time to veg and flower it all works off of that 12 hours of darkness every day (or night). You don't need a lot of money to grow but it seems like you either need lots of money or be ready to do lots of work. Be ready for one or the other.