The floor beneath the toilet is collapsing from a slow leak.

Not unless you are very handy. The toilet needs to be removed and then replaced after the floor is replaced.

What type of home do you have and what is it made of..........? - Do you have insurance cover? Get Experts Price for job before considering a DIY. It will help you realize what has to be done.

I don't think you should you need a Plummer to 1st fix the leak the leak is costing you to have a high water bill , then the plummer can fix the toilet my your friends can reefer you to one .

Well, are you handy? Removing the toilet and resetting it is not difficult; and there are many vidoes that will show you how. But you are going to need to replace the flooring and since it is collapsing; possibly support underneath it. It is on a lower level? Do you have crawl space or a basement you can look underneath? Are you sure it is from just water damage; are it could also be termites. I have had similar damage where they had to put a section of my house up on "jacks" to lift it up to replace a support beam. I would have a professional look at it.

Yikes! If you have at least some construction experience, I would least attempt to fix, but line up a contractor just in case. You will need to remove the toilet, and probably replace, and rip up the floor to see how extensive the damage is (hopefully not the joists), and see if water has worked its way up the walls yet. If it has, those portions will need to be replaced too. If at anytime you feel in over your head, call in the pros. Good luck!

You need to remove the toilet. Cut out the damaged floor. Replace with new wood, flooring, and replace the toilet.

probably not, the commode will have to be removed, the damaged floor cut out, new flooring put in & the commode reinstalled, then new floor covering, and if you can't match & piece in to match the rest of the room, you'll need to recover the whole room.

Only if you're very handy. You probably need to have the joists repaired as well as the flooring. Call a reputable contractor for an opinion and estimate