Im looking to buy a savage model 99 in 30-30 caliber from a friend. I'm not sure what to offer him for it. it is in 80 % condition. Any suggestions?

I recently saw several Savage 99's at local gun shows in about the condition you describe. They were tagged at around $475. Do you know it's year and model? There are several ways to get the year of production from the serial number on the Internet.

Well im not totally sure how old it is, but i know it has an octogonal barrel. so i think its relatively old/rare. idk.

If it is an original and not a commemorative model, I'd say it's more of a collector than a shooter.....

I hope the receiver has not been drilled and tapped for a scope. Also look for cracks in the stock at the tang. Another somewhat common way to reduce the value would be adding a recoil pad and shortening the stock.

I just went to a gun show today, in the whole building, I found 3 Savage 99's! Two were about 750 and the third was 699. At best, these were 80% condition.
The Savage 99 has become a rare collectors item down here! The last gun show that I went to last year, I found only one 99 in the building! It was a 30/30 at about 80% condition. The asking price was about 650! I will not give close to these prices for a Savage 99!
One word of caution: there are several models and grades of the Savage 99, and they were made up into the 1970-80's! There are big price differences between these rifles, so be careful and do your homework!
IMO, the Savage 99 in 30/30, defeats the 99's enduring quality; the box magazine!