If I understand you correctly, you are asking what is the best method for performing at a yard sale. I came to this conclusion because of the two quotes I've listed below.
no, see they would pay a quarter then if they liked it they could tip
I understand this to mean:
You pass the hat, they pay up front, you perform, then they pay again if they like it.
Let me rephrase the scenario.
You are a musician at a yard sale. You offer to play a song for a quarter (before the people have ever heard you perform). Then you play your song. If they like the song, they are encouraged to leave a tip.
Or you send me a quarter via PayPal and then I give you advice. If you like the advice, then you can send me more money. If you don't like it, bad luck.
Basically, this first version of "yard sale magic" could work. It would probably alienate the people visiting your yard sale and discourage them from actually purchasing any of your old, decrepitative stuff. But it could still possibly work.
My guess is that you could earn a dollar. Especially if other relatives come to your yard sale.
i could do it free, and have a tip jar, what do you guys think?
I understand this to mean:
You perform then pass the hat. They only pay if they like it.
This is the classical scenario. One factor of success depends on the number of people coming to your yard sale. The more people who come and are there at the same time, the better your chances for getting tips. However, I don't think you will have too many people there at one time. Mostly it will be a close-up show for a couple of people. Furthermore, people who go to yard sales are not usually in the upper-income brackets. That means they might not be as willing to part with their money in the form of a tip. In addition, if tipping for your performance is encouraged too much, they might be discouraged from purchasing any of your old stuff. However, it could work. My guess is that you can earn three dollars.
It also depends on your skill level. I can't comment on that. It also depends on your customer base, which depends on your neighborhood and the quality of the items your are trying to sell because they are no longer good enough for you any more. I can't comment on this either.
However, I recommend that you still perform, but do NOT put out a tip jar. Do magic to get those poor people into a good mood. This will help them part with their hard-earned money when buying some of your old, discarded stuff. Furthermore, it is a good environment to practice. My guess is that you can still earn 2 dollars and your family can sell a lot more of their obsolete, delapidated stuff.
Don't worry about the tips, worry about the experience.
(if you like my advice, you can send me a quarter via PayPal.)