One of the difficulties that I experienced is finding decent places with a secondary suite in my price range (under $350,000).  

The comps in this area range from 60K-150K.

Figure out what makes a good property actually GOOD and narrow your search range down to those.  

Can you be more specific zip, neighborhood,price range(all-in cost),Cap rate, area and property that definitely off the table and when were you looking to close

This will invaribly be different for each rate and scenario but just a general gauge.Even though rates are in the 3's and 4's the monthly payment or what we call the "mortgage constant," on our end is higher because your payment does not consist of just interest, but interest and and 1/360th of principal on a 30 year fixed loan which is designed to amortize/payoff to $0.00 balance by year 30 or 360 months.Typically a rate around 4's will have a monthly mortgage constant of around .50% monthly (6.00% annual) or about $500 per month for every 100,000.Sometimes when the rate gets into the high 3.50% range the MC is around .45% per month ($45 per month for every 10,000 borrowed) so it doesnt vary much while at 4.50% 30 year fixed the MC monthly is around .507% or $50.70 per month for every 10,000 borrowed.I suppose all this technical speak means is that if you borrow money where the outflow out of your pocket is around 6% with interest and principal considered then you'll probably want to reinvest it somewhere else where you can get considerably higher rate of return on this cash than 6.00% atleast this is how I look at it.If you want to make 6% + 6% for cost of funds then you'll want an investment with a hurdle rate of 12.00% or higher cash on cash as an example.

I hope you're investing endeavors are going well.Tough market right now in the area and price range I'm looking, low inventory.I found an off-market property from a landlord that's tired and wants the property gone.  

We just picked up a vacant property in Centerpoint, AL for $15k, and priced it to sell at auction, opening bid, $39,500, knowing ARV was mid to high $70k range & someone paid a buck more and we are happy clams, only a couple months.

I am familiar with the 1% rent rule which would imply that I should be looking to get around 3500-4500/ month for a house in this price range.  

they are both valued at the $20,000 range 

Scottlooking for properties in the 250-400 range that ARV +90-150k depending on scope of work to be done..