Can this be bad for PR - adding and deleting links every once and while. What I want to say is that I'm selling links on month, so I heard Google punish those sites. But how can they acknowelage that, is this the way - when they see lots of changes in links? Thanks.
It's definitely not a good idea to change all links every month. It looks unnatural and it's pretty easy for Google to notice that. It's strange that buyers are interested in just 1 month. They won't get a great benefit in such a short period of time. Try to sell your links for 3-6 months next time and explain to the buyers that it's a win-win solution You can even offer a small discount for longer periods...
according to google webmaster guideline, you need to place a nofollow attribute to links that you sell (then again, who would pay for a nofollow link?) if you sell links however, make sure you dont advertise link sell on your site and sell links privately. removing and replacing few links on an occasional basis is fine as long as there is no major changes.
It is not a good idea. Google will not consider links if you remove. Instead of this you can get some quality links at low rates on long term basis.
Thanks for replies. No, I delete and add one or two per month, others are there on longterm basis. I told the buyer, but he only want's one month, what can I do about that nothing..