Outdoor grow- plant and leave it?

I have a friend who wants to do an outdoor grow this year, but I am concerned about how he wants to do it. here is what he told me about:

Wants to grow plants in a cornfield. Therefore, he wants to wait until the corn is about knee high and plant knee high weed. He believes the corn will be knee high in early July. Anyone know for sure, when corn gets knee high? LAter or sooner?

He also wants to just plant the plants and leave them on their own until harvest time. He claims that visits to the plot are basically prohibited. That means no watering, no fertilizing and no sexing/chopping down males. I STRONGLY urged him against that, due to the decreased yield and the inability to address problems that may arise. but, he said he wants to do this out of security concerns, since he plans on doing the grow on someone else's land without them knowing about the grow (yes, I know that is a stupid idea, but...whatever).

I am concerned about the tendency for marijuana to grow faster and higher than corn. Is this something to be worried about? He plans on planting a bunch of bagseed, since he's too lazy and cheap to get quality genetics through the mail. Therefore, he has no way of knowing the characteristics of the plants he will be sowing.

The overriding philosophy he has is that he wants to just grow the plants to 1-2 foot tall seedlings and plant them in the cornfield when the corn is the same size. Once in the ground, he will leave the plants until harvest in early to mid-October. He believes that the marijuana will grow at the same rate as the corn. He will not be watering or fertilizing the plants at all. He believes that the farmer who works the field will not notice the extra crop being grown, since the last round of fertilization will be done in late June and he believes the farmer would not go out into the field again until late october or November. Is that true for growing corn?

In the end, I think the idea isn't the greatest for reasons that are self-evident. But if you can point out any major concerns that my friend has to address would be appreciated.

Any other tips would also be appreciated.