Starting with the best wishes for all of you, I'd like to emphasize the importance of sterilisation of tools, pots, growing medium when you start seeds, amend soil, a.s.o.
I'm "cooking" the ingredients in a pot at 80-120°c in the oven for about 30min to minimise the levels of pathogens, fungi, etc. I'd like to think that this is my small scale solution, time intensive but cost effective in the long run.
You want to make sure to bring "the good guys" back in, aka EM, worm juice and the likes.
If on a budget with money, you'll have to put in the work and time.