contractors and landlords please help answer this

[Varinder Kumar]

My tenant wants to purchase a welding unit and  ends a 220 volt outlet for it. The AC unit is plugged into a 220volt outlet but it's not accessible.
1.Is it okay to get a 220 volt out installed? 

2. My tenant said he would pay for it, and WA to to know how much it would be. So how would I go about setting this up legally? 

3. Should I accommodate him in the first place? 
Please advise as I want to take the appropriate steps.  Thanks y'all.