I think all of the questions listed above would be off-topic for this site, because they fall outside the purview of gardening fair and square.
1) Is it legal in Canada to sell surplus beans outside my house?
We don't deal with legal issues on this site.
2) Is it best to wash and scrub my surplus carrots before offering them for sale?
Produce sold for consumption is regulated differently in different countries. Since most (if not all) folks on this site are home gardeners and not commercial farmers, the answers are bound to be incomplete/inaccurate/misleading/subjective.
3) Which surplus crops are likely good sellers?
Subjective, off-topic and besides, candidates for "good selling crops" vary from region to region depending on the local climate, culinary tastes and economy.
4) What's a good way to gauge the right price for selling a surplus?
"Right price" requires a knowledge of demand and supply in the local market. This depends on the local economy and is off-topic for a gardening site.
5) Do I need to state the weight of any fruit sold loose?
This is again a legal issue depending on where you live. Not related to gardening.
It is important to distinguish between the science/art/hobby of cultivating/working with plants in the garden and things a gardener does with his surplus. While the former is of interest to most gardeners, the latter is of interest only to those who happen to live in the same area, grow the same crops and have a significant surplus to think about selling and as such, is also localized, in addition to being off-topic.