DIY Setup - step by step

I found 40x Kyocera 210 Watt for sale for $20 a pannel. Is that a great deal? I have to install solar panels on my house because I want to build an ADU. ( I'm in SD, CA ). I think buying an inverter like that : https://sungoldpower.com/products/6000w-48v-hybrid-solar-inverter-split-phase-120-240vac?variant=42834846613641
Based on the spec, the system should be able to produce up to 8.4kw, but the more realistic number is around 149W per panel or 5960W total. It's fine if I don't use 100% of my pannels' potential. I'll add batteries later, as I don't have the budget right now.

Is my thinking correct, or am I totally off?
Thanks