Don't forget the tithe either. 10% to the lord, 10% to the church, and 10% to plant next year. Then you had to keep the rats, mice, weevils, and water out of it.
But of course the farmer would also be raising sheep, goats, chickens, and other vegitables to supplement his income and keep his family fed. I seem to remember much of the larger livestock could be communal livestock but the chickens and like are probably his.
So I could see a reasonable assumption of about 1£ (ie 240d) a year.
So running with those numbers and assuming the default monetary system: 1£ = 1 lb of silver = 100 sp. That is about 2cp a week, but with no additional property costs (other than repairs).
I'll have to run the numbers some more, but that doesn't look too far from Old Man and my estimates.
Of course that also assumes a £ is 1 lb of silver, which wasn't always the case.
It kind of fun playing with these numbers ☻
-Pyrotech