I would think it'd be pretty simple to calculate his actual rent income based on the properties current conditions and explain that at best, the tenants in place stay for years to come, he continues doing the bare minimum, and his highest predicted income is x dollars, barring any emergency spending to keep the tenants happy.

This 4plex is in a class C or D neighborhood (not exactly sure which) but my realtor and I saw the potential in it due to the cash flow/COC numbers we calculated and the fact it had a ton of work done to it in 2017 to get it to decent shape (all new electrical, furnaces, HWHs, renovated apartments, new roof, all doors and windows, etc.) 

They have a strong background in finance and are skilled in preparing proformas, calculating returns, and underwriting deals.

Quote from @Brad Helmink: Oh, also, I used the BP projected rent calculators on a few new properties they've sent me, and their estimate was quite a bit higher so be careful there.

I am not an economist but I also know they "changed the rules" when calculating inflation and used to account for the borrowing rate in that calculation which they no longer use (which would have let us know inflation was around 15%+ recently at the peak and not 9%). 

My outstanding loan balance is 163K @ 3.5%I calculated that I'd clear 900/mo after expenses.I was planning to buy my new house for cash, but with the market where I'm moving/buying I'm having to go about 100K over what I was planning, so I'm taking out a 50K loan for that property.

Well this is where a simple IRR calculation comes in whereas if you invested $100k and got $40k back today, to get back to even would be 8% over the next five years.

That lien needs to be added to the cost of any refi, and changes the calculation when or if a refi makes sense.

The number usually varies from 10-20% depending on credit score, property analysis, etc.Some lenders will work with any level of investor experience, credit scores as low as 660 and can close in as little as 10 days (there are loan options for 640-660 credit scores- they require 20% down).Another good thing is interest only and 6-24 month loan terms- you can refinance by selling or refinancing to a long term DSCR rental property loan at any time once you complete the rehab.Once the property is ready you can sell it or if you want to keep the property as a long term investment, you can underwrite the loan based on your income /debt to income (DTI) ratios or you can go the DSCR route where the loan is underwritten based on the actual or market rents from the appraisal.DSCR loans won't use your income to underwrite the loan.DSCR loans are based off of down payment, credit score and either actual or market rents so it helps to supercharge an investor's real estate goals and net worth.Here's a bit more in detail about how rates are calculated for DSCR loans:1.

The golf sim will help garner more bookings but I do not think you can count on it to generate a specific amount of revenue.The ADU I would get real world prices on cost from a GC and then calculate the return based on other units with ADU in your area or if no comps you can get an idea by +1 the bed and bath and looking at larger comps in your area.