One big challenge potentially is volunteers. Charities and foundations tend to attract willing like-minded people.
With zero exceptions, if you take on volunteers, do so for only two circumstances:
1) special projects where providing all requisite supervision and resources adds to and doesn't detract from your mission and necessarily have a defined timeline
2) in systemically sustainable long-term roles where you have the requisite resources and desires to supervise them.
Lots of charities run off 2 people or so, are constantly busy and see all the good more hands could do. They see willing hands, and jump at the opportunity. For the first day or week or maybe month, things work out but increasingly the time to manage and oversee the volunteers takes away from the mission, or you reach a point where you don't have enough volunteers to sustainably expand your reach, so their volunteering is just taking away from your work, which then leads to mutual burnout.
If you take on volunteers, expect to need to spend a ton of time managing them. Until you get really good at managing volunteers (and it's a different skill than managing employees), expect them to take up most of your time. Your challenge is to learn ways to scale their involvement to serve your mission while undergoing the massive turnover and reliability problems volunteers bring (and be ready to write endless letters of recommendation).
Allowing others to help out for free with your passion will completely and totally transform your organization. If you go that route, do so because it's what you want, understanding it will completely change everything (most obviously your role). It's ok to tell others you aren't in the position to effectively use their help.