okay well basically here are your challenges
- SLI doesn't work well. Among other problems, NVIDIA has to manually patch their drivers to support each game. Unless it's a high profile AAA game they don't bother. And since SLI usually doesn't deliver the kinds of performance improvements that people expect it will, they might not bother even if it is popular enough - they'd rather say SLI is unsupported than have SLI actually reduce performance for their most spendthrift customers. So, SLI won't help you. Flight simulators and VR games aren't popular enough that NVIDIA would bother whitelisting them in the first place. What you'd really need is a single fast GPU to play games. You'll also want that GPU to run in PCIe 16x mode, which probably isn't going to be possible in a multi-CPU computer you can reasonably afford.
- You're going to need a motherboard with at least five PCIe 4x slots. Technically anything should work in a 1x slot with reduced performance, but NVIDIA cards aren't designed for it and might fail to initialize. They probably make specialized motherboards for mining now. You'll need one of them.
- That means you're going to need a CPU with at least 20 PCIe lanes available for GPUs in a 4x/4x/4x/4x/4x configuration. Consumer-grade Intel CPUs only have 16 lanes. Even the newest ones. You're looking at something more like a Xeon Gold or HEDT on the Intel side, or a high-end Ryzen or a Threadripper on the AMD side. A regular Intel CPU isn't going to cut it.
- 5 two-slot blower GPUs aren't going to fit on any motherboard ever. You'll need to buy a specialized case for GPU mining that can properly cool and support the GPUs when connected to the motherboard with PCIe risers or extension cables. The cards are designed to be supported by the slot, so yeah, you can't just, like, install them in a huge case after the motherboard ends. You'll need a special case that can support them. The alternative to this is to fabricate custom water blocks to convert each GPU into a single slot GPU. Then they might fit.
- If the above costs more than $3000, it is cheaper to buy a single Titan V.