Central air system with indoor blower & outdoor condenser generally don't come with pre-charged lines so self-install without certification isn't really an option in US.
Having just installed a mini-split in my office shed with a pre/charged unit. I told him it was easy and helped him. We ended up needing to buy an extra long line set to make the distance work, which needed more refrigerant.
I called 15 different places and finally found one that could come out and charge the line for under $350. Which was hard to stomach with the whole unit costing only $750 from Amazon.
Around here anyway, I was getting quotes of 20k for the install & equipment of a central air handler and the outdoor unit.
I'd be dead before the thing paid for itself in electricity cost savings. $20,000 ÷ (~90yrslife - 40yrsold) = $400 / year of neccesary savings to break-even as my casket is lowered into the ground.