Inherited Pool Problem?

Mi wife and I bought a house in New Jersey 2 years ago. The house has an in-ground vinyl pool for which we don't have much information available. The previous owner had lived in the house for only 3 years, and did not really know when the pool was built. The problem we are seeing now is that it looks like every year one side of the pool is caving in a couple of inches per year. The attached pictures show the state of it as found we we opened it this year. What I would like to ask, what are the options we have if we wanted to keep the pool. Thanks!

Could it be that for some reason the top lip of the pool is not attached any longer to the wall? The separation is located on the wall closer to the house. Please advice....

Ariasc, welcome to the forum. I believe your assesment is correct. From the pictures it looks like that section of coping has become unbolted from the wall of the pool and the liner is pulling it into the pool. As long as the wall on which it sits is still sound, you should be able to reattach it. If you want to give it a try yourself and have any ?s as to how to do it and things to watch out for, post it here and I'll get back to you. The fix should take under an hour, so if you'd feel more comfortable hiring a local vynal pool company to adress it, the cost shouldn't be exorbitant.
Good luck with the pool and hope you get to enjoy it all summer with no more problems!

Thanks for your reply... Right after my initial posting, I wanted to cycle the water thru the filter, only to find out that the motor is shut (due to heavy oxydation)... The new motor (Hayward HP 3/4 HP) will be delivered tomorrow...

If you look at the picture a little bit closer, you will see what appears to be a ripped metal piece (Is this the coping?). You mentioned that reattaching the coping to the wall is OK as long as the wall is sound... Does it get attached using bolts? Please advise!!!
If I want to fix it right; I would like to add a second return line for a permanent vaccum and maybe add steps to it and change the liner.

Yup, that metal peice is the coping. One of your pictures gave a good crosssection view, the first step is to remove that blue strip (put a screwdriver in it and lever the end up, wear gloves as there can be some sharp edges involved and be gentle, it's flimsy aluminum). You will now be able to see the channel through which the bolts are secured - yours probably aren't anymore but 1 might be hanging on. Be careful not to allow the peice of coping to go into the pool, it could rip the liner, if possible have someone help you - all they have to do is hold on to one end of it to keep it from going in the pool while you are reattaching it. You may have to take the liner out of the track to get the coping to go back into it's original place, at the angle the coping is now it should come out easily (if you have any trouble getting it out, just ask me, I'll tell you how to do it).
Here's where preparation comes in handy- before you start playing with it . Procure a drill, a 5/16 hex bit for the drill (one with a 3 - 6" shaft is optimal), and about 20 5/16 'tech screws' about an inch long (They have a special tip that drills through metal). Pull the coping back in place (it should have a lip that will 'lock' on the wall - if not, just keep it even with the adjacent peices) You sholud be ready to start tacking the peice of coping back in place. (The old bolts may have ripped the track a little, try to pound it down flat to the top side of the wall and start screwing) ** BE VERY CAREFUL WITH A POWER TOOL THAT CLOSE TO A POOL FULL OF WATER!!!** - I don't want you to get hurt, if at any time the screws won't go in, try another spot. Rather than trying to 'bull' the screws in, put firm, steady pressure on the butt of the drill and squeeze the trigger in 1 second bursts, this seems to facilitate the drilling action of the screw. Place the screws about 1' apart and stagger them in the track (ie #1 on the pool side of the track, #2 towards the deck side, etc) secure the 2 ends first and fill in the middle ones.
I hope this is enough to let you tackle it, if not repost and ask for whatever clarification you need. I realise that this doesn't parse well, but in the time it took me to type it, I could have made the repair and gone for a swim ;)