It is one of the early Sarouk design, 1910 - 20. Condition as you posted yourself not good, but if you get it for 300.00, it is ok (What else would you get for 300$ :-)?). Just make sure it has no dry areas, then even 300 is too much.

I would not pay amy more than 300 for this rug. 700 is too much. The yellow areas are probably animal urin, there you should look for dry spots. If you pick up a corner of the rug when it is laying flat on the ground, and move it up and down quick, so the air flows under the rug, it should move soft. If there is any area stiff, fold the rug together and see if the cotton will break due to the preassure. It makes a sound sort of like opening a peanut. If you buy a rug like the one you posted, a wash is a absolute must since you never know what happened on it before. (I recommend to have any rug washed you buy from private anyways).