There's a store of information on the web - including on this site - about how to structure seller financed deals and about common pitfalls.    

Look at the web site  oceanfrontguru.com, you will get an idea about market. 

It adds up.) or free ACH payments  through  a company called "DWOLLA", however DWOLLA had a lot of negative reviews on the web, and I don't want to spook a tenant.- I settled on Cozy.co where I can automate tenant applications and screening and keep track of payments and accept electronic payments through ACH, or debit or credit cards the tenant pays.Hopefully, TurboTenant will provide free electronic payment and accounting/tracking.  

It's web-based so no losing excel spreadsheets or having to update various copies. 

But it is ok with you to gamble with your money sending a ton of mailers and 3%  will contact you?

Web based- that way you don't need to do software updates.

They will have the systems and experience that goes the xtra mile to uncover as many unknowns as possible, get as close as possible to reliable numbers, and know what that work and energy and execution is worth, which I know to be $$$$.Otherwise, it’s just a gambling exercise between less experienced guys or frankly ‘advantage takers’ hoping they are something they aren’t, and there’s no cheat code to that. 

You're going to talking to them face to face or on the phone, or sending someone a letter, or they're looking at your web site.

I would like to have someone design my own web site for rent collection.  

When applying for business credit many creditors check on your address to see if it’s a home address or a PO Box, look for a web site, can they find your phone number through a directory check (411) or online.