Before the window even opened, United had committed funds to one of the most expensive arrivals in the club’s history, Brenden Aaronson.
Marsch was then reunited with more former players in Rasmus Kristensen and Tyler Adams as the American started the build a team for Premier League sucess.
Alongside Luis Sinisterra and Marc Roca, young prospects Sonny Perkins and Darko Gyabi were added to the roster - with potentially more players yet to arrive.
Thus far, the near-£100m spend has been covered by the big-money sales of Raphinha and Kalvin Phillips - but how does their net spend measure up to the other teams in the top flight?
Here we take a look at the expenditure-less-income of every Premier League team, ranked from biggest to smallest...
13. Aston Villa, - £14.04m
Smart business by the Birmingham side this window, as Brazilian superstar Philippe Countinho became a Villa player for good and Seleção teammate Diego Carlos also made the switch from La Liga. | Getty Images
14. Bournemouth, - £10.71m
Save the addition of former West Ham United full-back Ryan Fredericks, Bournemouth have raided the Championship for all their incomings so far. | Getty Images
15. Liverpool, - £4.59m
One appearance, one goal, one trophy - Liverpool’s £64m man Darwin Núñez is already proving his worth. | Liverpool FC via Getty Images
16. Leeds United, - £623k
Jesse Marsch has been massively backed with a total spend of nearly £100m, but the departures of star duo Rapha and the Yorkshire Pirlo have nearly covered the bill. | Getty Images
17. Leicester City, £900k
The Foxes netted less than a million for the sale of one of their most loyal servants and are yet to add any players this window. | Getty Images
18. Brighton and Hove Albion, £13.4m
The sale of Yves Bissouma has more than compensated for the Seagulls’ spend so far, with Julio Enciso and Simon Adingra so far the only arrivals. | Getty Images