Queen, I reread your advice in detail and I want to go look at junipers now. As far as tools I own all kira's .. I work in It but was trained in culinary. There is literally no sub for good steel. I have bought a lot from superfly bonsai and their soil is great. I know I can get it cheaper but I live in a townhome. I dont have the space for 'cheaper materials' so I pay prepack.
Anybody have a garage cold box details?
I also live in a townhome. I've been doing bonsai here going on 30 years now.
A few things I've learned about having bonsai in a tiny (30x 30') backyard:
Choose species according to what will do well in your area. You've mentioned redwood and serissa. Both will be a problem in Zone 4. Serissa will have to be overwintered indoors from first to last frost. Redwood is a nickname for a couple of species, if you mean Dawn Redwood (metasequoia), you may be able to overwinter it outdoors-you're at the low end zone limit for its hardiness. As bonsai, trees tend to lose a zone of hardiness because their containers expose roots more directly to the the environment. If you're talking California Redwood (Sequoia sempervirens), you're going to have issues as it won't survive outdoors in Zone 4 winter, and keeping it inside will weaken it and kill it over time. If you have a garage (I don't) you're in a better position to keep more marginal trees as garages can be kept warmer (but too warm sometimes)
You're going to have to consult local bonsai people about overwintering specifics in your area. Don't rely on things you read on the Internet from people who don't live in your climate.
Avoid species that need coddling (any kind of elm, or if you have to keep trees indoors--ficus, are great tough, resilient beginner trees). You don't have the space for things that can't hack your environment. Search out the hardiest varieties--Japanese maples may be marginal in Zone 4 if you don't find cold hardy varieties.
There is no shame in buying prepared bonsai mix from good suppliers-particularly if you have less than ten trees or so and they're smaller. I used to mix my own. A hassle, dust, cramped storage, etc. make it more trouble than it is worth.
Maximize space--for instance ---Overwintering pits--I have a two foot deep, 8 x 4' pit I dug to sink trees into during the winter. I built a two foot tall wall around the top with decking posts. I use decking boards as a lean-to roof in the winter. In springtime, I lay those covering roof boards flat over the top of the walls of the pit and have a platform for trees to sit on. I also set benches over mulch beds that double as overwintering beds.
Hang heavy duty warehouse shelving from fence posts if you have a fence. That can double your area for keeping trees. If you don't have a privacy fence around the area where you keep your trees, expect theft.
Monitor your backyard sun exposure--find the areas of shadow and sun. Use them to your trees advantage--depending on species. In your zone, you'll want as much sun exposure as possible.