First of all, hi!
I am currently working on my research paper and trying to explain 2 dimentional variable : volume and instrument of corporate debt financing. Independent variables that I believe must be included in the model are specific caracteristics (capitalization of the company, debt to equity ratio, may be rating) market conditions (corporate spread over t bonds of bill, may be amount of corporate debt financing) and of course specific caracteristics of the instrument maturuty and covenants.
The questions are: a) Which proper model can be used (besides multinominal probit and logit).

Question

First of all, hi! 
I am currently working on my research paper and trying to explain 2 dimentional variable : volume and instrument of corporate debt financing. Independent variables that I believe must be included in the model are specific caracteristics (capitalization of the company, debt to equity ratio, may be rating) market conditions (corporate spread over t bonds of bill, may be amount of corporate debt financing) and of course specific caracteristics of the instrument maturuty and covenants. 
The questions are: a) Which proper model can be used (besides multinominal probit and logit).