Honestly - public school pre-k (most start at 4) are very good these days. I am someone who went to Montesorri pre-school and gained a lot from it but I would not hesitate to send mine to public pre-k.

If you want that strong base wait until it is time for him to go to Kindergarten then apply for assistance.

Also I prefer Montesorri over Waldorf muchly muchly.

I understand that you want whats best for him but you being an active and involved parent, reading to him daily, and helping him be creative are with much more than a private education - You rock.