I would do remote dev using vast.ai and other cheap cloud computing resources to ensure you want to do this and have utility for it, then build your own. 3090s are typically the most budget friendly, and if you have any IT chops (and tolerance for noise), then server rack-mounted hardware, PSUs, and riser cables tend to be the most efficient with tons of PCIe lanes (which is a hidden issue people have with consumer-grade gaming PCs as they scale).