New Renter First Month Rent and Security Deposit Handling

[Brice Alef-Torrisi]

Hello Everyone,

I recently bought a 3-unit investment property in Michigan and have plans to rent out one of the units to the sister of one of the neighbors. I have her staying in the one br while we renovate the other unit she wants to move into so I can begin collecting cashflow. She moves in mid-June so I collected the Security Deposit and First month's rent ($1200 sd + 800 for the 1br). I have a couple of questions. Do I prorate the amount for her first month in the one-bedroom and then charge her the full month's rent for the following month? Secondly, how do I deposit the Security deposit into my account from Venmo in order to keep it separate from my other funds? Lastly, should I continue collecting rent through Venmo or should I have her set up automatic payments with my bank? 

Thank you very much.