I'm thinking of buying more properties for a downpayment in the near future, but it might affect and impact to my ongoing second mortgage application.

I think it will be unlikely to find a commercial-style loan for a multi-family property at anything less than 20% down...they will likely be 25% or more at this point. 

If you are new to renovation, don't let people trick you into thinking things like adding a bedroom is easy or warranted.

There are other residential in the neighborhood so zoning i don't think would be an issue. 

I will give you the numbers then tell you mu strategy idea. house purchased for 415,000 in august of 2020 at a sub 4% rate but I treat it as 4% because I am not 100% sure what the rate is (I am getting into contact with realtor soon don't worry)The house could rent for 2,500 per month at minimum and I think I could get 2600-2900 but not 100% sure.It is now on the market for 600, 000 but I think I could get it to 575 since it has been up for a couple months.well 575,000 at a 7% APR is way higher than the rent so I was thinking I could do a seller financed route.

What else should I be thinking about?

My parents live in the Katy neighborhood.It is very safe and from what I understand, has a good school system.A lot of the homes are 'newer builds' since it is still a relatively new neighborhood.You are also in downtown houston in about 30 minutes during non-rush hour times using the I-10 highway.I don't think you can get the 1% rule anymore in the area but close to it.Since the homes are newerish, hopefully the property won't have too much renovation / repair costs.Best of luck

If you think they'll shrug you off, you'll be surprised.As you figure out the best strategy for you and what these deals look like, you can start meeting with investor-friendly agents to help guide you further and start analyzing deals. 

Therefore, I think I'll be placing heavier emphasis on cash flow markets.

I think you should consider how to comply with the TCPA first.