That and being honest about how much value you are bringing to the table. If you don't actually improve on the free version, it is unethical to sell.
And you should never use language to imply a value proposition where there is none. For example, someone else posted a link to some green card scammers. One of their claims is:
> "USAFIS GUARANTEES 100% participation in the Lottery!"
This may be true, but it is still an unethical statement. It hints that this is a net positive vs. the free application the USG provides, but in fact any valid, submitted application participates in the lottery.