It depends on the loan program. For Owner-Occupied Lite Doc programs, see below:

LTVMin. Reserve Requirement
Less than or equal to 65% LTV0 months PITI(A)
Greater Than 65% LTV3 months PITI(A)
Borrowers who own other financed properties are required to evidence an additional 1 month of PITIA reserves for the subject property for each additional financed property, capped at a maximum total of 18 months PITIA reserves.
Reserve Requirements
* Reserve requirements apply to subject property PITIA only.
Owner-OccupiedInvestment
CLTV <= 65%0 months PITI(A)Loan Amount Less than or equal to $500,0003 months PITI(A)
CLTV > 65%3 months PITI(A)Loan Amount is between $500,001 – $1,500,0006 months PITI(A)
Loan Amount Greater than $1,500,00012 months PITI(A)
*Cash-out procees may be used and applied towards Reserves, if:
1) LTV is 70% or less; and
2) FICO is 720 or greater.
*Cash-out procees may be used and applied towards Reserves
* Borrowers who own other financed properties are required to evidence an additional 1 month of PITIA reserves for the subject property for each additional financed property, capped at a maximum total of 18 months* Borrowers who own other financed investment properties are required to evidence an additional 2 months of PITIA reserves for the subject property for each of those properties