Five hundred square feet! Mmmm, that is a big area. Actually there is no easy way to remove an existing tile floor. You might even earn yourself some nasty little blisters on your hands too if you are not wearing gloves to protect them. Then again, the easiest way to do this, is to hire a professional tile contractor to come in and do it for you. But, if on the other hand you want to save a buck and do it yourself, you will need a hammer to begin this project. First you bring the hammer down onto an area of floor where you want to begin. Chip away at the first tile until it is completely removed. Once this is accomplished there is a tool that looks somewhat like an ice pick which is made specifically for slipping under and popping out old floor tile. This may take a little time, depending on the mortar underneath the tile. Some may come up easy and others may not. Once this step is complete you may need to rent a hand held grinder to grind down the tidbits of mortar that remains on the subfloor. Also you will have to explain what you need the tool for to the person you are renting it from so he can provide you with the right grinding accessory for the job. After all the bull work is done you are on your way to laying your new tile flooring. Another good tip for this project would be to go to (www.diy.com) for more specifics on how to do take on such a task. Good luck and, have fun!