Question about rust and frames on 3rd Gen 4-Runner

Hello Community.
This is my first post. I am seriously considering buying a 1999 SR5 with 179,000 miles Vin# JT3GN86R7 X011 5651. Car has spent its entire life in southern CA or Phoenix AZ. I am wondering the following:
1-What exact area of the frame on these cars were most notorious for rusting through to the point of causing a safety issue? Anyone can point out a very specific area that I need to inspect in an attempt to see how weak / rusted that area of the frame is?
2-Since this car has not seen snow and salt in its life, I am thinking of putting an aftermarket type of rust inhibitor on the frame and under-body. Any good recommendations out there for the best product? Is this even a good idea?
3-I know for sure the timing belt has not been replaced on this vehicle. I researched and found out that the 5VZ-FE motor is not an interference motor. Does anyone know if there is any real urgent reason that should cause me to do this repair urgently before the timing belt breaks? Meaning, will it be much harder to do the replacement if the timing belt breaks prior to the replacement? Also, when I do the replacement, what other parts are an absolute must for me to replace while I am in there?
Hope ya'll can help out the newby here.
Thanks much
Darin from Chicago

 

The first two comments in this thread have what you need most likely, these guys know a thing or two. Chances are high you won't have much of a rust problem.

A lot of guys say POR-15, lot of guys say Eastwood...seems to me that its a matter of time and money available. I have no idea what to do for frame treatment and its something I'm still looking into

Hopefully someone else can help with you timing belt question, I don't know enough yet sorry.

 

Also do you know when the lower ball joints were replaced? That will be something you will want to ask the owner about when or if they've been replaced. On 1st gen Tacomas and 3rd gen 4Runners, when the lower ball joints fail its pretty catastrophic. Just a bit of safety and peace of mind to know when they've been replaced

 

If the frame is relatively clean and is solid, id hit it with fluid film or whatever equivalent product you choose and call it a day. Clean up the underbody and recoat every year prior to winter and the frame should hold up nicely.

One thing you may want to do when you first get it, if you do purchase, is run a hose into the frame and do a good rinse to try and free up any crap inside before you let it dry out real good and hit the inside with rust protectant also, preferably when it warms up in summer. 3rd gen frames are just as bad as 4th gens for retaining dirt/debris near the rear trailing arm mounts and rusting out. Shouldn’t be the case if the vehicle is from the southwest but you never know if the PO has been driving through mud or whatnot.

Products like POR15 and Eastwood rust coatings are what I’d consider the final assault on rust, not something you use for prevention.