For additional financing requirements to be provided by a second mortgage, the best second mortgage options are going to be institutional for rate and private for leverage.

Instituational rates will likely be 2 percentage points higher for a second than an institutional first mortgage.  So for a 1st mortgage of 4%, the second mortgage could be as low as 6%.

For higher leverage amounts, institutional lenders will not typically go higher than 70% loan to value.

Private lenders, on the other hand, can go as high as 85% loan to value if they like the property and basic profile of the applicant.