To expand, a fixed salary is generally based on a daily wage, such as $600 per day. For a 4-day work week and 2 weeks vacation, this would be $120k per year.
If being paid on production, you can expect 25%-33% of your production. If being paid on collections, you should expect(or request) a higher percentage, such as 30-40%, because a practice's collections are going to be lower than production, for the most part.
The ideal way to be compensated would be a fixed daily rate OR percentage of production, whichever is higher. The production-based pay is incentive to produce more, while the fixed daily rate saves you if the front office isn't getting you enough patients, and it gives the front an incentive to get you those patients because they don't want to pay you if you are just sitting around.