"Money is not allowable for the Sakyan-son contemplatives, the Sakyan-son contemplatives do not consent to money, the Sakyan-son contemplatives do not accept money, the Sakyan-son contemplatives have given up gold & jewelry, have renounced money. For anyone for whom money is allowable, the five strings of sensuality are also allowable. For anyone for whom the five strings of sensuality are allowable, money is allowable. That you can unequivocally recognize as not the quality of a contemplative, not the quality of a Sakyan son.
"Now I do say that thatch may be sought for by one needing thatch, wood may be sought for by one needing wood, a cart may be sought for by one needing a cart, a workman may be sought for by one needing a workman, but by no means do I say that money may be consented to or sought for in any way at all."
http://www.accesstoinsight.org/tipitaka/sn/sn42/sn42.010.than.html
It would seem that what is required for subsistence is allowable. However even hoarding robes is making a profit, above what is required for oneself.
Unlike the actual material, money can be used in ways which are detrimental so it makes sense to limit it in a community where its improper use brings disrepute to the entire community (and where many types of individuals with various levels of morality are part of).
The great ‘product’ monks can sell is the Dhamma. It makes sense to put limitations around that, because of this. Being invited for a meal and then being asked to give a dhamma talk slightly circumvents ‘selling the dhamma’ dynamic.
Lay people have other means to obtain money and the whole point of lay life is being able to enjoy sensuality (at least, as it was seen in the Buddha’s time…). If a lay person is doing more than this (ie- being a kalyanamitta to others) and teaching the dhamma, it is commendable, as long as they are not misrepresenting the dhamma.
When money or profit comes into the picture the problem is that the dhamma will be altered to make it more appealing. Then the issues of misrepresenting the dhamma comes into play.
The question then is how can a lay dhamma teacher ensure that what he teaches is in line with the dhamma? Having said that even honest monks who live a renunciate’s life might not be very accurate in their dhamma teachings.
Charging money is only an issue if there is no other source of dhamma (and the teachings are accurate). Since there are other sources, it is down to the person listening whether they want to pay for this particular teacher’s instructions or not.
Some lay people might feel that the dhamma is sacred. They might feel no amount of money can pay for the teachings they deliver.
If a lay teacher is good at teaching, teaches accurate dhamma in line with the early texts, does it out of compassion and not looking to make a ‘killing’ (ie-‘profit’) I see no reason why they cannot charge for the dhamma (or ask for donations) for -costs, to free them up from employment to do more useful dhamma work, to support loved ones who would loose out otherwise, electricity, water etc.
This is my opinion.
with metta,
Matheesha