Please advise-15% down or 20% down- gift money issue

[Rhondalette W.]

I am in the process of purchasing my 2nd and 3rd properties with conventional financing from the same lender. Originally, I planned to put 20% down on both properties because I thought that it was a REQUIREMENT that investors put down 20% on conventional loans. Next, the lender explained that I needed to have 6 months reserves for each property so I asked my mother if she would give me the money for reserves. Mother agrees and wires the money into my account. Then lender says that they can not use "gift" money for reserves in the purchase of investment property which means I do not have enough money to put 20% down on both properties with 6 months reserves for each. 

Next, the lender suggests that I only put 15% down on each this way I will have enough to purchase both properties on my own and have enough for reserves without the use of gift money. However, if I only put 15% down, I am financing more, which increases my monthly payment $15 over 30 years and I will have to have mortgage insurance PMI of $30 a month. This cuts into my projected cash flow from rents $45 each month, so I am not happy about this. The lender explained that I could send some of the gift money with the first mortgage payment to immediately get rid of the mortgage insurance-PMI but this would still leave me with higher mortgage payment that is $15 higher each month.

Questions: 

• I didn't know that investors could only put down 15% instead of 20% on a conventional loan is that standard?
• Is it better to use more of financing (using other peoples money) with only 15% down. It doesn't seem like a better deal since borrowing more increases my monthly payments.
• Gift money rules- have you all ever heard of the rule that gift money cannot be used on investment purchase? How long do I keep the money in my account before it is not longer considered a gift?
• Do you see other options for me in this scenario? Should I only purchase 1 property, use a different lender, finance both at 15% down etc.