[hardflex]

I have an older house about 1000 sq ft that's been rented but now vacant and as part of the rehab and other considerations my wife wants to install a forced air heat/ac system. It currently has a wall unit gas heater and window unit a/c's.

I have a chance to buy a working used system at a good price. My sense says the gas heat has not gotten more efficient in the last few years, the A/C prob has. I'm thinking the gas mechanisms are very reliable with few working parts, so maintenance is not a factor there. The A/C newer and probably more efficient than the unit in the larger house i live in now, so the savings on the more efficient system would be negligible.

Is there anything I should know about the older systems vs newer ones?