Rental arbitrage is scam or not

[Ryan Daulton]

I had somebody contact me about investing in their rental arbitrage. She said that if I pay $42,000 for the next 18 months, that she guarantees I will at least get this 42,000 back by the end of 18 months but probably much more.  It would cost me only $2300 per month which includes rent utilities furnishing and property management. 

she showed me one example only of a customer who profited greatly. What sorts of questions can I ask her to learn how much risk this is? 

although I'm skeptical of going with her service, it is pretty logical because she would be helping me rent out a property long-term but sublease it for Airbnb. Since Airbnb rents per day are much higher than LTR, there is great profitability.