While everyone talks about Jan 20, it's likely that Trump is already in violation of the Emoluments clause and other government regulations, in much the same way someone already winning a tender can't go against the conditions of that tender in the days preceding contract signing without voiding that award.

Especially since US law basically works under expectations of precedent, and precedent says overwhelmingly that the Electoral vote is a formality, and that the winner of first Tuesday in November is immediately endowed with all the rights of the presumptive new President, including security briefings, assistance with the transition, a secret service detail, etc.

The government is paying $9.5 million for the transition plus other fees like secret service, so Trump is already receiving federal dollars (since he doesn't pay taxes, obviously the only part he pays is anything he explicitly picks up). Elizabeth Warren already flagged the GAO a month ago about potential problems with conflict of interest and such (expressing implicitly that these violations might be hidden under the "chaos" of the transition).

Expect of course that the Republicans will give Trump a free ride, and contrast with the fury and obsession over the vandalism or pranks on Clinton's departure of a whopping $15,000 damage, which among others took a full time GAO employee 9 months to investigate, so guess government cost of at least $100K to put to rest the obvious. Similar to Comey's obsession over Martha Stewart's $40K trade while hundreds of billions went missing. BTW, for those who think Comey's just a misunderstood public servant, he was a hedge fund trader among other activities with net worth of $11 million and a cherry $3 million home in Connecticut. And he previously investigated the Clintons on Whitewater and the Marc Rich pardons (along with the original Marc Rich case). Seems 3rd time on emails was the charm - not for proving anything, but the desired effect.