I personally use propwire.com for residential lists but you can get them online from tons of places. 

I typically use regional banks to fund my deals but my 2 go-to banks have either slowed or fully stopped investment loans so recently I've connected with several online brokers but all came from ads or they reached out to me vs personal recommendations and intros so I have concerns. 

You will find many resource here that are more than willing to help you out with just about anything.I am a broker on the lending side of things and have a fairly solid presence in TX. 

As mentioned already, there are lots of great property management apps out there that have online rent collection features.

She does not have an on line mangement system though just sends a check each month with a little ledger of expenses.I have a client that runs a larger company and they do a nice job at least on all the deals I have done for them as a capital partner when I do the draws and look at my before and afters they do some really nice work in a timely fashion

Look online to see if any properties are being offered for sale or rent with a legal basement unit and you may get a tip off.

This is not something you will get online you need an attorney to draft documents and it is just a matter of whether you draft them or their attorney drafts them

Send a letter giving them your/pm's contact and a detailed explanation on how to pay the rent (Helpful with older residents if you are going from check to online billing.

Create an Online Presence: Build a strong presence on Facebook, Instagram, and a credible, professional website.

Online title search companies.