30 ft- one roof air sufficient?

I'm in the process of buying a 30 ft. Class A. It has one roof air conditioner. I think is a 1355 BTU. I haven't seen it. The owner lives in Arizona. He says it does ok when in the high 90s. He doesn't the HK ts wired for 2 air conditioners. Is it a mistake getting this? It's a pretty good deal and the exact floor plan we like.