Impact of fees on LBO Model (IRR, MoM)

Let me see if I can answer this briefly/quickly. 

There are two types of fees 1) M&A fees (also known as advisory fees) and 2) Financing Fees. We'll focus on #2 as M&A fees are paid during the transaction and have no real impact on the actual holding period/operating model build

Typically financing fees are x% of total debt raised. So for instance if you raised $100m of debt your financing fees would be $2m (assuming 2% of total debt for this example) and that $2m would fall within the B/S as a contra-lability (or for modeling purposes you could put it on the asset side). 

Your financing fees are generally amortized over the same lenght as your debt item (typically 7-years). So following the same logic above you would amortize $2m/7 = ~$0.3m annually. This amortization will flow into your income statement as an amortization expense but you will add that back in your CFS as its a non-cash expense but within your B/S you will should see your financing fee decrease by $0.3m each year (based on the assumptions above). 

It would have an impact on your final EV as less cash (albeit miniscule difference) is being generated because of this ~$0.3m financing the business is paying each year.