You should be able to realize your $200/month goal with just 3 GPU’s, and right now if you can even get a mining motherboard, they are prices upwards of 400% MSRP.
Motherboards mount to their cases/frames using standoffs. Often, there are more standoffs than holes in the motherboard to screw them down. These extra standoffs are easily removed. If not removed they will short out the motherboard prompting some to set motherboards on cardboard.
While PCIE lanes are important to large volumes of traffic, I haven’t had any bottleneck issues splitting one X1 PCIE lane into four USB outputs to Riser Boards. If your (cheaper) motherboard doesn’t have many PCIE slots try these: They are excellent.
Amazon.com: Runxin PCIe 1 to 4 PCI-Express 16X Slots Riser Card PCI-E 1X to External 4 PCI-e USB 3.0 Adapter Multiplier Card for Bitcoin Miner (1 Pcs): Computers & Accessories
For the highest quality Risers 9s, 10s, you should consider these using Coupon Code: " RedPandaMining "
March 8th Preorder – GPURisers.com – Newest Version Riser 6-Pack - GPURisers
Don’t want to try NiceHash, HiveOS, SMOS??? Here are a few good miners you can add your address to.
PhoenixMiner 5.5c - AMD+NVIDIA GPU Miner 
Releases · trexminer/T-Rex · GitHub
Releases · develsoftware/GMinerRelease · GitHub
Wallets:?? People dealing in Crypto have wallets on their phones. They are also available for desktops.
BitPay is available for online shopping payments in Crypto
BitPay – Do more with your Bitcoin
Atomic Wallet: Many coins, atomic SWAPs, easy to use:
Atomic Cryptocurrency Wallet (atomicwallet.io)
Zelcore Flux Wallet: Many coins, swaps, I’ve only used the desktop wallet. Supported on Discord
Zel is a zk-SNARKs Privacy Based Cryptocurrency Powering the Zel Ecosystem, giving users control over their privacy through cutting-edge zk-SNARKs private addresses.
Crypto.com Wallet for mobile (mobile only in USA) Gives the advantage of spending crypto on your visa card. Beats paying all those fees sending coins to exchanges. Not a fan of CRO but the basic card should do. Also an Exchange which is a BONUS.
Crypto.com - The Best Place to Buy, Sell and Pay with Crypto
OK, I’ve added my input. Happy Mining, and also realize that profits vary greatly all the time. So slow starting until you get the hang of it is wise.