Specifically, I'm interested in finding a lender that allows a 10% down payment on investment properties.If anyone here has experience investing in these areas or has any lender recommendations, I'd greatly appreciate your insights.

I recommend networking with other investors and asking for personal recommendations, using companies (not individuals) with strong reviews on Google, etc.

Do you recommend turnkey investing?

I wouldn't recommend trying to get into real estate to solve immediate financial needs.

I would definitely not recommend this.

Has anyone ever use them or is there another company recommended?

I recommend that you have a PM in place before you leave.

I have some clients that are interested in looking at Condo/Townhouses in Houston as an investment, but I'm not sure what to recommend they withhold as Cap Ex from their cashflow when running the numbers.

If this will be your first property, I'd recommend not making it a section 8 property at first.

If you can find a duplex or 3-4 unit property that makes financial sense with the necessary down payment and reserves then that would be my recommendation.