In terms of paying someone to find a tenant, it seems I have two options:1) A real estate agent (the one who helped me buy the place)2) A tenant locator service (apartmentsnow)What's the best way to go about this?  

Read up on the 50% rule...with vacancy, maintenance, Capex, etc you're losing money even with it rented at $1500 per month.IMO I would pass because it's not a good deal to start with, sorry.

Currently renting out the old primary residence at $1800/month with a cashflow (after mortgage, insurance, taxes, vacancy, maintenance, cap ex, etc.) of over $500/month; with the other two investments each pulling in between $250-350 a month.I also decided to make tennis my "full-time" job and pursue real estate more heavily as my career.

Those refineries, and oil service workers will return. 

Most of the SFH for rent with decent looking yards around here the landlord pays for lawn maintenance (or lawn maintenance "included" with rent if that's how you want to look at it) for exactly this reason.  

My mom wants to partner with me and buy property together since she has perfect credit and a better chance at being taken seriously by the banks that will give us a mortgage. we are going to go 50/50 on the down payment and all expenses/maintenance. we will be getting an fha loan and putting 3.5% down which will allow us to have a big emergency fund.

Find a lender/broker who is very familiar with these loans and you should be fine.You do not have to pay the fee if you are a: Veteran receiving VA compensation for a service-connected disability, ORVeteran who would be entitled to receive compensation for a service-connected disability if you did not receive retirement or active duty pay, ORSurviving spouse of a Veteran who died in service or from a service-connected disabilitysource: https://www.benefits.va.gov/homeloans/purchaseco_l...Source for how much your funding fee  will be:  https://www.benefits.va.gov/homeloans/documents/do...Curious as to why you are exempt from property taxes.

Getting a feel for some of the expenses (occupancy, Cap-ex, monthly maintenance) will be tricky at first, but feel free to reach out or post for some guidance on if what you are assuming is correct.

Some services offer a great price, but it's only for 1 photo - which is not useful for most properties.4.

There may  be some smaller agencies that would be interested in buying your services as well.