Advice/Suggestions for a 220v AC unit

I saw someone asked the exact first question I was going to ask, which was 'what is this plugin' so I already know for sure it's a 220v (or is it 240? I've seen it being called both.) My question now is, does anyone know a good AC/heating unit that uses this plug and will cool down or heat at least most of a 1200 sq ft old house? I've been googling around and it's looking like they're all going to be $500+. My place is 100+ years old, built sometime in the early 1920s. It has vents in the ceiling for gas powered central heat and there's a spot off the back porch where someone clearly had a central air unit at some point, but it's not been there for a while. One of the previous owners had this plug installed in the dining room right under a window and I was told by the guy I'm purchasing the place from that it was for a larger AC unit. I'm definitely looking to get one of those soon because as of right now there's only 2 places in the house a regular 110v unit can be plugged in and both are too far from my bedroom to actually get much of any cool air flow to me and a fan isn't cutting it (I live in Louisiana, summers are brutal.) My room is off the dining room though, so getting a bigger unit in there should help my room a lot.

As a side note, can I buy a tester somewhere to make sure this plug works before I buy a unit? I had electricians out last year to give me a quote on some electrical updating and I asked about testing the outlet but it wasn't something they were willing to do without me paying them for the entire rewiring job first (which isn't something I can't afford yet, hence not having a place in my room to plug in a unit.)

Thanks for the help!

I saw someone asked the exact first question I was going to ask, which was 'what is this plugin' so I already know for sure it's a 220v (or is it 240? I've seen it being called both.) My question now is, does anyone know a good AC/heating unit that uses this plug and will cool down or heat at least most of a 1200 sq ft old house? I've been googling around and it's looking like they're all going to be $500+. My place is 100+ years old, built sometime in the early 1920s. It has vents in the ceiling for gas powered central heat and there's a spot off the back porch where someone clearly had a central air unit at some point, but it's not been there for a while. One of the previous owners had this plug installed in the dining room right under a window and I was told by the guy I'm purchasing the place from that it was for a larger AC unit. I'm definitely looking to get one of those soon because as of right now there's only 2 places in the house a regular 110v unit can be plugged in and both are too far from my bedroom to actually get much of any cool air flow to me and a fan isn't cutting it (I live in Louisiana, summers are brutal.) My room is off the dining room though, so getting a bigger unit in there should help my room a lot.

As a side note, can I buy a tester somewhere to make sure this plug works before I buy a unit? I had electricians out last year to give me a quote on some electrical updating and I asked about testing the outlet but it wasn't something they were willing to do without me paying them for the entire rewiring job first (which isn't something I can't afford yet, hence not having a place in my room to plug in a unit.)

Thanks for the help!