Have had my Makita 2030 for more than 20 years. It is cast iron and built to last. I have put 1000's of feet of poplar and maple through it and it keeps going and going. I am still using the original planer and jointer knives, just sharpen them occasionally. The only thing that wore out are the planer rollers. I had Western Roller recover them ($135 in 2001) and they are as good as new.
You certainly should look at it before buying if you can. Run some wood through the planer and see how the rollers do. If the rollers are worn out, you will have to push on the wood hard to get it through the planer. Also check the planer table to make sure it goes up and down properly. If it was abused, it may not operate smoothly.
I paid $1,250 in 1984. I would say that $1,700 for one used is way too much to pay. I could be wrong but I dont think the 2030 ever sold for $5,000. A more reasonable price would be $500 particularly if it has some wear, if the rollers need to be recovered and if the knives need replaced.
If you can get it for less than $1,000 and it is in good shape, I would buy it. It is a work horse. The jointer is a joy to use and having the paner right there makes it doubly good.