When you become licensed you subject yourself to your brokers supervision and the oversite of your states licensing board/department.

I understand the purpose of the GC position isn't manual labor, but that still feels steep for simple supervision, especially considering the budget is tight. if this was a school/hotel/restaurant/etc I could understand. do GCs normally charge both a weekly rate and a flat percentage on the end for single-family jobs?

It's hard to supervise by phone unless you could acquire a general contractor you really trust. 

Typically all real estate activities of a licensed individual need to take place under the supervision of your brokerage.

And most kids don't play well without adult supervision. 

You were not equipped to supervise this project in the manner you chose to, but you took the burden on.You're goddamned right the landlord "distanced himself" during the renovation. 

Who will supervise the remodeling?

Asset managers frequently supervise other property managers.The individual building manager may be employed by a property manager or directly by an owner, and usually manages a single large property.The resident manager may be employed by a real estate broker or a managing agent or an owner to manage an apartment building on a part or full-time basis.Essentially, a broker's license is required if you do any advertising, leasing or collection of rent.

https://www.thetaxadviser.com/issues/2012/dec/clinic-story-06.htmlIn determining whether the income should be classified as ordinary income or capital gain, the court evaluated nine criteria: (1) the taxpayer’s purpose in acquiring the property; (2) the purpose for which the property was subsequently held; (3) the taxpayer’s everyday business and the relationship of the income from the property to the taxpayer’s total income; (4) the frequency, continuity, and substantiality of sales of property; (5) the extent of developing and improving the property to increase sales revenue; (6) the extent to which the taxpayer used advertising, promotion, or other activities to increase sales; (7) the use of a business office for the sale of property; (8) the character and degree of supervision or control the taxpayer exercised over any representative selling the property; and (9) the time and effort the taxpayer habitually devoted to sales of property.

If it's the same Agent or the same Broker supervising both Listing Agents, you MIGHT have a better chance, but I wouldn't bet on it.