This allocation should be based on the fair market value of each component, typically determined through an appraisal or the values agreed upon in the purchase agreement.

It affects the marketability/value of the property. 

I avoid the multi-family market here, so unfortunately, I will not be a good go-to here, but I am confident you will find quality resources and help here on BP.  

Try networking locally with HML's who know the market. 

If you like where you live, I would explore investing in a cheaper out-of-state market. 

Educate yourself on the local market, network with other investors and agents, and always have a solid plan in place before making any investments.

I would skip this and buy a 4 family with below market rents and raise rents and do value ad to get rents up to market!  

The price we thought was very reasonable in this current market based off the other properties we have seen prior to that with similar layouts. 

Lenders do not look at your personal income or debt and will use the current market rent or lease (up to 120% if the lease is significantly higher than market rent or vice versa) as qualifying income.

Just be sure to account for the upfront costs, ongoing maintenance, and market demand to make sure the numbers work for you.Good luck with your decision, and feel free to share updates as you move forward!