Answer: Congratulations on your first garden! I think you'll find that as your successes mount and your enthusiasm grows, you'll expand your garden as the space allows. Veggie garden need lots of sunshine so choose the sunniest spot you can find. The concern I have with the area you describe is that flooded ground is often more compacted so you'll need to remedy the cause of the flooding so it doesn't happen again and you'll also need to thoroughly dig the area and add some organic matter (such as compost) to help loosen the soil and make it drain well. Or, you could build raised beds and fill them with topsoil. Raised beds will help keep your dogs out of the garden if you build them 18-24" high. Dogs learn pretty quickly that they're not supposed to jump up into a garden bed.
As for growing veggies to sell, check around at local Farmer's Markets to see what crops are available. This will not only let you know what grows well in your area but also what shoppers are most interested in. Most communities have Farmer's Markets so visit a few and ask lots of questions. You may even be able to fill in a gap - fresh herbs, for instance.
Best wishes with your new garden!
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