1) By solid top do you mean just a flat solid board covering the top of the hive? That would be a little unusual to me, usually the top cover sits down like the lid of a shoebox, which means you can put a shim (a small piece of wood) to prop one side up enough to make a crack for airflow.
2) I would say add a second deep first, its what I do. Otherwise you're going to have to use a queen excluder to keep the queen from laying in your honey super, and that can cause problems (enough problems that many experienced beekeepers simply don't use excluders in the first place except for very specific needs). More brood space typically means more bees, which means bigger/faster harvests. You could go straight to a honey super, but I think you'll encounter more problems and worries than you would by waiting for them to fill out a second deep.
3) I started with one hive, so its definitely doable. Its just easier with two. You're going to have a hard time finding bees this late in the game, most people know to order their bees early because there is always a shortage. I put my orders in back in December. However, there are other options. You could build swarm traps (many different ways of doing that, see the swarm board for more help there) and try to catch your own free-bees from feral swarms. Its not guaranteed by any stretch of the imagination, but when it works its free. Swarms should just be starting up in your area, so this would be the perfect time to get some boxes out there.
I've got links to plans on how to build nucs from plywood on my blog (and all you have to do is double the width of the fronts/tops/bottoms to make a 10 frame box). You can get the wood for one for just a couple of dollars at any home improvement store that sells lumber, so they're cheap and relatively easy to build. I wouldn't recommend trying to make permanent hives out of them, but they're great for swarm traps and temporary housing until you can get the money up for a more robust hive setup.
http://harrisonbayhoney.blogspot.com/2014/02/this-is-my-nuc.html
2) I would say add a second deep first, its what I do. Otherwise you're going to have to use a queen excluder to keep the queen from laying in your honey super, and that can cause problems (enough problems that many experienced beekeepers simply don't use excluders in the first place except for very specific needs). More brood space typically means more bees, which means bigger/faster harvests. You could go straight to a honey super, but I think you'll encounter more problems and worries than you would by waiting for them to fill out a second deep.
3) I started with one hive, so its definitely doable. Its just easier with two. You're going to have a hard time finding bees this late in the game, most people know to order their bees early because there is always a shortage. I put my orders in back in December. However, there are other options. You could build swarm traps (many different ways of doing that, see the swarm board for more help there) and try to catch your own free-bees from feral swarms. Its not guaranteed by any stretch of the imagination, but when it works its free. Swarms should just be starting up in your area, so this would be the perfect time to get some boxes out there.
I've got links to plans on how to build nucs from plywood on my blog (and all you have to do is double the width of the fronts/tops/bottoms to make a 10 frame box). You can get the wood for one for just a couple of dollars at any home improvement store that sells lumber, so they're cheap and relatively easy to build. I wouldn't recommend trying to make permanent hives out of them, but they're great for swarm traps and temporary housing until you can get the money up for a more robust hive setup.
http://harrisonbayhoney.blogspot.com/2014/02/this-is-my-nuc.html