I am in the process of building a 5-unit retail strip center in Mobile, Alabama.

Depends on your market, your desired scale, and your exit strategy.SFH:Easier to understand and pricePricing set in competition with other owner-occupantsEasier to sell off in pieces and at retail pricesMore systems to maintain than MFH all things being equalHarder to scale than MFHHigher rents per doorAll systems usually tenant maintainedMFH:Pricing set by profitability (cap rate)Exit strategy generally only other investorsEasier to maintain in larger numbers than SFH all things being equalEasier to scale than SFHLower rents per doorSome systems maintained by youThere's no answer to "which is better".

The idea is that investors think differently than retail clients, and are looking for different knowledge and assistance from an agent.  

But Have to be aware and compare that most of the time (depending on area and on this market) Retail buyers or the "market" is paying a bit more for as is outdated houses ( so you check for those)  and also Check updated houses cos the ARV(After Repair Value) will increase what the market will usually pay for a better condition and modern house. 

How to find qualified real estate broker/agent in South Florida who's expertise is working with real estate investors and not just retail clients? 

Real estate is an industry where there are time things move at a fast pace and spans of slooooow boredom.

I've been in the retail automotive business for 20 years and I'm in my late 40's. 

Yes, a retail store won't buy at spot, just like they won't sell at spot.

You have to wait for her and be patient cos it has to be at her own pace and with no pressure other wise she will resist. ( I dont know why, but in general women are wired to protect and conserve) And all she sees when you tell her about RE is RISK and PROBLEMS. ultimately is the fear of the unknown. ( She is protecting her household) Automatic reaction. 

That's exactly why it is a powerful strategy and if you're willing to live with that reality for a while, it can help pay down your mortgage and build equity at an accelerated pace.