You need to check at least one landlord prior to their current.

Prior small business management experience.

While this is traditionally a slower period than Jan - Jul, it is clearly must slower than in prior years.  

That's even after checking on them prior to giving bids.One bad instance on a sub:We were at a full rehab helping finish because the guy and his crew were to close to the dead line and there was too much left to do.

Also, although thousands of apartments were completed over the past two years, rental inventory remains less than the level prior to the conversion boom, when the metro also had 120,000 fewer households.The surge in apartment construction is also providing an outlet for some of the equity pursuing acquisitions in the metro.

Should we begin interviewing potential PMs prior to purchase to ensure we have one ready to rock once the house is ours? 

I am glad that I questioned the POA's prior to getting checks, but no matter how this is slice as you stated that this was not an easy business.

I would gladly push it off for a few months to keep an already vetted, paying, good tenant in.Plus, like @Kevin Leonce said, if you're worried about lease up, start advertising a little earlier to get a signed lease prior to his move-out. 

Yes, I do choose an appraiser to appraise the property prior to listing.

My HOA requires a signed lease contract prior to the HOA background check and interview process.