If you want oodles of cash, plant wheat and sell it at 1 to get more mats (silo and land expansion) and barn.
Expand your silo as much as possible. If necessary, buy 1 coin worth of wheat from people you find in the newspaper, fill it with wheat and only wheat, and visitors will only ask for it. That’s where the money comes from and comes in.
There will come a time where you don’t need to plant wheat. Just purchase it from other players to fill up the silo and cash it in.
Another tip is to grow crops of high value only and keep selling it. Buy wheat and other good deals from your friends or in the newspaper.