It's like pest companies trying to capitalize on the crawl.space enclosure market, research it and you'll discover a wealth of differences.

Probably a combination of issues; perhaps "fishing in the wrong pond" for subs, a few miscommunications with a quote from a sub based on a description as opposed to an actual inspection,  from an owner that, not being an AC person may miss relevant issues, are these new or used units, did the handler "fit" into the enclosure, etc.  

I have some construction experience (but no expert) and on several of the houses we have looked at, I suspect a patio enclosure or addition has been added without a permit.

I have a buddy who is a shower enclosure salesman.  

If he has to move and suggests he will trash the place, give him a 24-hour notice to enter every two weeks with the excuse you are going to do some repairs...find something simple you can do like caulk around shower enclosure and do it meanwhile conducting a visual inspection to see if he is causing damage. 

I bought 6- 2x4 by 12 feet long and a ladder and my nailer.Took my work truck and backed up with a 2x8 on my tailgate and another 2x8 along the side of leaning Pisa!

As we are looking for prop #2 right now, I'll probably try to do the enclosure right before we move into our next property so I can immediately start paying off the cost of the addition with the increased rent. 

Learn how to properly evaluate rehab costs, spend lots of time in Home Depot/Lowes pricing materials like flooring, cabinetry, plumbing and electrical fixtures, doors, base and case, shower enclosures, etc.

A search on BP might even find links for this since I recall posting it previously.One other reason I have encountered in the City of Phila is that the electricity for the fire alarm system must not be fed from a meter that is a tenant meter (since the tenant power could be shut off due to non-payment).I don't think this will run as high as 10K unless you are doing lots of re-wiring.You will need an extra meter; since you say it has four, I'm going to guess you might have to replace the four-meter enclosure with a larger enclosure that is able to handle at least five meters.

No enclosure on that one, i don't usually put them in unless i have to.