Just do not put anything like, advertise here, buy a link?. If you keep it to a reasonable amount then there is no need for the 'no-follow' attribute, otherwise the person buying the link won't see the benefit.
Yes and no on that one, lots of people claim to have made many thousands of dollars with MFA sites bringing in folks with cheap keywords and getting expensive outgoing clicks.
Buying or selling text links will not affect your website ranking in any way if you do it the way it should be done. Selling links to the relevant sites will not hurt you in anyway, dont sell more than 5 links per page and don't mention anything like sponsored links or paid links on your page. Buying links is a must for SEO, you can never have your site rank high without quality inbound links. Anyone claiming its bad does not know anything about links or they dont want you to achieve good ranking. I've been in text links business for a long time now so i know ins and outs of this industry.
Who has time for reporting?...play it right and you'll be safe all the way. No one could ever tell the difference in paid or non paid links. Just stick to relevancy and check the quality of the site you are linking to.
There is a lot of Philosophy is what your saying. But it hardly applies to real life. It's a waste of time arguing this.