In my layman's point of view, this is co-mingling and alter-ego violations to piercing the corporate veil. 

You will have to refinance into an LLC/Corporation/Trust that your wife owns and she will be the guarantor.

And there are people who probably work 2 hours a day in some corporate job and are paid 40.  

For many folks in your position, the only real advantage to an LLC is if you want the pass through entity with a partnership/S-corp or the anonymity aspect.

I'm assuming you're considering hosting travel nurses or maybe corporate housing that exceeds 30 days and intend to leave it fully furnished & charge nightly rates similar to STR?

You need to build relationships with corporations.

I also have experience with retail, both my wife and I started and used to run a clothing shop while we both were busy (me with my company and she with a corporate job), for around 5 years before we decided to sell it.

Then reinvest all the profits for myself and the money lender until we reach a future goal ($600K).The question is, if the money stays within the LLC then I assume that I am paying roughly 20% corporate tax on all profits from each project.

Full time happens with 100+ units and often you see people scale a business on the side, like PM, construction or something unrelated like a resort in Costa Rica ;-) I am no different - I "retired" from my corporate career in 2015 and quickly realized that I can only watch so much daytime TV. 

Great advice above from the GOATs of the MTR forums.I would add that you should also try to get on the lists of corporate housing and temporary housing for insurance companies.