PM fees typically run 8-10% of monthly rent for a duplex plus often a leasing fee of 50-100% of one month's rent when placing new tenants.

Typically in many jurisdictions when it comes to this type of niche there are very few who do it and they all work together. 

i agree that a new purchase at 75% equity will typically not have significant cash flow and may even be negative when properly allocating for all expenses.Investing to max equity without reserves is risky and you indicate would result in stress.  

What color are you?"

Do you typically reevaluate your current returns based on the net equity you have in your properties?

Has anyone with experience of multiple valuations in Portugal got a view on whether banks typically under value their valuations as a norm or not? 

Studies typically cost $3,000–$5,000 but affordable DIY options (around $400–$500) exist for simpler properties.

The sales comparison approach is typically done for residential real estate and will be less appropriate and come in under value because there are no good comps, and even an appraisal using the income approach (unless the appraiser is trained to do more complex commercial appraisals) is probably not going to be the most accurate either because they typically use market cap rates and in this case you don’t have good comparable income properties to find the market cap for the analysis.  

@Austin TessMany lenders have a seasoning period (typically 6-12 months) before you can refinance.

Rates can be very similar to those of conventional financing (Fannie/Freddie - full doc loans that you will need to prove income to get), but typically a little higher than conventional financing. 2nd - Networking and partnerships!