Something simply doesn’t compute.
Your parents are unemployed and you have $50,000 in assets - that would mean 100% tuition at Brown.
Do you parents have stocks, investments?
How have they been living for the past 6 years?
Do you own your house outright? If so, you’re not expected to sell the house, but to use HELOC - something that doesn’t exist in France, but exists in the US: you get a loan with a favorable rate based on your house’s equity value.
Did you fill out the FAFSA and CS Profile right?
You’re not a French citizen, right? Otherwise you could check if you could get a “bourse du CROUS” - you’d have to register with a French university in the math section, something like UMPC I suppose as Math isn’t “contingenté” and I don’t think Physics is, and show up for exams in order to keep your grant. After a first year in Math and Physics with some CS and English, you’d pick “parcours bidisciplinaire intensif” in Maths and Physics.
http://www.upmc.fr/fr/formations/diplomes/sciences_et_technologies2/licences/licence_st_cycle_d_integration/mipi.html
http://www.upmc.fr/fr/formations/des_licences_a_la_carte.html
If you have French citizenship, you could contact them and see if you can still register.
From a concrete standpoint, it allows you to get a grant while at Cambridge in exchange for 4 days’ presence per term in Paris.