Modular homes can indeed come with garages, either pre-designed or as an add-on, depending on the company you choose and your specific design plan.Companies and QualityThere are numerous reputable companies that produce modular and manufactured homes  Examples, 1) Blu Homes, 2) Clever Homes, 3) US Modular Inc..

All complimented with Amazon fulfillment centers, google, and more tech manufacturing jobs.The bad reputation of “Detroit” comes from OOS investors wanting sub $40,000, D class properties in poor condition, because they pencil out to 2-3% deals on paper.

Direct with seller (Through their own marketing)  they typically have more control of the seller and also more often have a reputable title company the usually work with . ..   

Being consistent, ethical, and providing value will help you build a reputation in the industry that can lead to more opportunities. 

Seeking recommendations for reputable agencies, and I'm curious to explore options beyond Glass Casa Inc.

It costs the same to have a plumber snake a drain regardless of the value of the house.

. :-) I found the realtor from BiggerPockets, and he seems to have a solid reputation.

If you have a few good subcontractors - electrician, plumber, appliance guy you can handle most of it. 

The ones that always come through with good a reputation, reasonable cost and terms are the ones you would like to build a relationship with and work with them on future deals.    

A good PM isn't cheap however I want to point out that they may be worthwhile for the simple fact (among many other things) that most reputable PM companies will employ all the hotel staff which takes away a lot of employer risk (employee lawsuits) off the owner's shoulders.