If it is just a single family, then the income it produces will have less of an effect on the sale price as your primary consumer will be an owner occupant.

You can increase rents according to how much the consumer price went up.

Then, for those sponsors not particular 'proud' of their returns they would opt-out and you will be left with an incomplete data set to truly aggregate against. 

Most of the time they will just opt out of your emails, at that point.

Setting rent prices is not like setting the price of a consumer good - say milk - where demand is going to be far more inelastic and generally static over time.

If it bothers you, block the sender or opt out.

Writing a note each time is time-consuming.

Wholesale is a very effective method, is just extremely time consuming (until you have real processes in place) but you are fresh out of college, the one thing you have is TIME and if you put time and effort in wholesale you will be successful.Also as an optional step you can explore getting your real estate license so that when you buy properties you can get commission or help friends and family and get commission there as well.Credit is important when you don't have much cash, but more important than credit is understanding your options and what path you want to take. 

I know several landlords who do door to door collection and it’s so time consuming.

I've been lurking here for 10 months consuming all that I can.