I'm currently renting a townhome and seeking to purchase a househack when my lease expires, maybe a duplex or triplex depending on how the numbers work out. 

After filling it with my purchased items a couple times it was pretty much a normal rehab.If it's a listing, you could try to find a cleanout company that will agree to be paid out of escrow, or there are lending programs that offer home renovation loans to fix up homes to be sold.Be careful working with wholesalers as an agent.

If a potential tenant in this order recieves lease agreement then makes payment including security deposit, first and last months rent  via certified cashiers check is the agreement valid if it’s not signed? 

The documentation that my lenders require are typically tax returns (last 2 years), rent roll of all properties, personal financial statement, and leases on the subject property. 

@Jessica Muto I personally believe instead of hiring a property manager, you should vet a team of sub-contractors or some general contractors to handle the repairs, and get a good education on the landlord/tenant laws and the lease, then you can market the properties yourself.

@Jan Halasz all of these items are negotiable. 

If an owner agrees to a lease option contract.

My properties currently are managed by a property manager but I would like to move to managing them myself.How do you suggest I go about eliminating the management and introducing myself to the tenant and hopefully get them to re lease up again with me?

I put in my lease that I will be replacing the furnace filter, batteries for smoke detector/CO detector, and inspecting the unit every 6 months.

My lease(and most leases) specifically prohibit tenants doing repairs.