I would just keep it in the garage until you can get something like this.

Here is a link that might be useful: $500 Vinyl Shed

In the garage or basement if you have one with a walk-out door. It should not be stored outside in the elements.

put it on a pallet with a wash tub over the engine.

I think much of this depends on your climate. Where I am, you mower would be a moldy mess if you put it out on a pallet. A larger area certainly stays more temperate and is less susceptible to ventilation issues. With that not being in the cards, a small shed or even modified big dog house/play house off Craigslist put in the right spot of the yard could be fine. 1)Dry as possible 2) Located where out of the direct sun to avoid large temperature swings 3)Ventilation

Thanks for your replies. I had not considered ventilation. That little shed would be perfect - looking for a sale now.

if you haven't found shed yet, check costco