rusty ripple

you didnt mention the most important part, what kind of budget are you working with? ideally a separate location that is a building up to code and with plenty of lighting and electricity would be ideal, but thats ideal...
do you have a welding machine? i would say just start with your lean to idea, i would (and did) start with pipe holding up a roof supporting structure with a tin roof on top. once you get started, the beast will tend to grow on its own. adding more metal to metal is easy, but also i just dont like working with wood, confuses me, two boards to line up and you cant just weld across the gap or beat it into submission, but i digress.
i wouldnt recommend trying to get building permits as i know in my case, it absolutely wasnt going to get approved, which brings me to another important point...
how well do you get along with your neighbors? assuming the structure is safe(not a fire hazard, or not likely to fall on someone) there is little reason for a building inspector to show up, unless someone calls them to complain. so if you think your neighbors may complain, go ahead and get some permits and do it right.
at least thats the way it is down here in bass ackwards Louisiana, a good friend of mine works for the city in land use and zoning and shudders everytime she she sees the "structure" (building isn't quite the right word, i may get around to posting pics, but frankly, im a little embarrassed, whatever, it gets the job done, roof with tools underneath)

if drilling and tapping, use a carbide bit, and use a drill size a little bigger than you would for mild steel. probably want to use spiral taps as well, they tend be harder to break. i usually use a 3/16 inch bit for tapping mild steel, but then my drill press is a pos with a lot of runout so it comes out just about right. i forget offhand what size your supposed to use for 1/4"x 20, i think a no 7? go up 1/64" from that and see how it works. pretty sure machinery handbook has drill sizes listed according to the % of thread you want, but i dont have it nearby.
if you're looking for drills and taps of every single variety and material, look to msc (Industrial Supply Equipment from MSC Industrial Supply) or macmaster carr. msc has a wider variety, mcmaster carr is easier to use.

i dont really follow that. you lost me with bend the inner web to 90 deg and flatten the back.

just to get started i would recommend a 28 oz ballpein and a 2-3 lb cross pein any brand will do. you wont be able to tell the subtle differences between hammers at first and you wont get miffled when you learn why not to use an expensive hammer on a hot cut hardy.

its easy to get overwhelmed in the beginning of almost everything if you try to digest all information at once. eventually it falls into place.

an older anvil will generally have a work hardened face that's harder than the face on a new anvil. bigger is better, the more there is down there the more it hits back. peddinghaus is made in either germany or france and they are top notch, forged construction, you cannot go wrong with these and they should be cheaper over there than here.

what did you make the scribe and center punch out of? are they treated and annealed? i ask only because if their not they will drive you nuts, which would be a shame, there is something wonderful about using beautiful custom made tools.

check out the nomma website National Ornamental & Miscellaneous Metals Assn.

and of course in the background is a mouse, which may or may not have left droppings on the other side of some kind of a chunk of mystery metal

i agree with the fire extinguisher in bold plain view, even putting a big abnoxious sighn above it that says "this wasn't here in 1832, so ignore it unless you see a fire. why are you still reading this sign? there are more interesting things going on in the shop, if theres a fire and you're reading this sign you should stop reading and extinguish it, seriously by this point it might be too late and you should just run..." or something to that effect.

the rule of thumb in regards to anvil height is it should be at knuckle height if you're standing next to it making a fist. its better to have it too high than too low, to low and it will destroy your elbow

you can never have enough idea books lying around, art deco books can usually be found in the art or architecture sections of larger bookstores. they range in price but it is always nice to have reference material when you need it.

Try coming up with ideas at night.

is it to the right or left of that funny shaped anvil with a hole in it?

i used to have a shop, but it got destroyed in katrina so i've since moved it all into my backyard. the neighbors haven't complained yet but i try to have everything shutdown by nine. i've made things for some of them and that always helps make things run smoother. always feel guilty when i can hear them outside enjoying a summer night and i fire up the engine driven welding machine and the angle grinder, but since they know i'm still looking for a shop they are patient.