They strategically avoid speaking to customers and offer support via online chat to a non US based helpdesk.

I sent her a 5 day notice via certified mail with return receipt requested because she wouldn't answer the door or answer my phone.

I am still new to real estate investing and I'm eager to begin my real estate investing journey and build general wealth for me and my family via real estate.

@Tove Fox - Residential Real Estate InvestingPros:Lower Entry Costs: Easier to get started with less capital required.High Demand: People always need homes, making demand relatively stable.Easier Financing: Mortgages are generally easier to secure with favorable terms.Simplicity: Easier to understand and manage, especially for beginners.Flexibility: You can use it as a personal residence or rent it out.Cons:Tenant Turnover: More frequent turnover leads to vacancy and more management.Lower Cash Flow: Income potential can be modest compared to commercial properties.Emotional Buyers: Residential prices can be influenced by emotions, leading to price volatility.Maintenance Burden: Landlords often deal with repairs and maintenance, which can be time-consuming.Commercial Real Estate InvestingPros:Higher Income Potential: Stronger cash flow and higher returns are common.Long-Term Leases: Tenants often sign longer leases (3-10 years), reducing vacancy risk.Professional Tenants: Business tenants tend to take better care of the property.Valuation Based on Income: Prices are based on the income the property generates, not market emotions.Shared Costs: Tenants often cover property expenses like taxes, insurance, and maintenance (via triple-net leases).Cons:High Entry Costs: Requires more capital or partnerships to get started.Complex Management: More expertise is needed; you may need a professional property manager.Economic Sensitivity: Commercial properties are more sensitive to economic conditions.Challenging Financing: Securing financing can be harder, with stricter terms and higher interest rates.Zoning and Legalities: More complex regulations compared to residential properties.Key Differences:Risk: Residential tends to be lower risk, while commercial offers higher rewards but with greater risk.Management: Residential is easier for DIY investors, while commercial properties usually require a team.Scalability: Commercial properties are easier to scale, offering more potential for significant cash flow increases.

Tourist interest in the centre of Lisbon is enormous, so the option of letting via Airbnb is a viable one though they aren’t giving more licenses in these areas.

I do not care what the source of the return is  Historically the highest return is via a value add and appreciation and is more so recently due to the recent rate increase versus earlier this century (before 2022).However, most new RE investors cannot handle extended periods of large negative cash flow.  

I also agree that RE appreciation is unlikely to match the last dozen years, but you never know.Where I am unsure we agree is that paying $450k to improve the cash flow ~$3k (your numbers but I expect my delta wold be similar meaning both my cash flow estimates would be worse than yours but both would be worse by the same amount not affecting the difference) makes sense especially if the cost of having the extra $450k is only 6% rate which is historically simple to beat via numerous investment options and hopefully no one is investing in RE for an expected of 6%.  

Definitely online via property management software!

While I use it primarily for noise concerns (it alerts me for sustained +80 decibels), it's also handy for cigarette smoke and tracking temperatures (in addition to our Ecobee thermostat)- sensors on all exterior doors and possibly windows (which you might have via smart locks for the doors)- exterior camsA recent guest for reasons only known to them set the thermostat to cool and 60F in the winter (where it's currently a balmy 11F). 

More importantly, how’s economic occupancy via delinquencies?