As for whether you'd be responsible to take out a loan if an investor puts 20% down; unless you have another means of procuring the other 80% - yes. 

In Nashville, where my other properties are located the typical management fee is as mentioned 8-10% of gross rents, however, what I do see a lot of variation in is the "lease fee" the percent of the first months rent to procure the tenant.

Then they might even feel entitled to a procurement fee anywhere from 100-half a month rent to a whole month's rent or more in some areas. 

In fact, I would generally avoid most multi-units in South Florida unless YOU are the procuring buyer.

You also do not want to have the listing agent show you the property, thus becoming the procuring cause of the sale and then have your current agent jump into the picture.

However, the agent has exclusive right to sell (whether he procure the buyer or not, he's entitled in comission).

Procuring cause.

Once you do decide to procure your first rental, definitely lean on the BiggerPockets community as a resource; I'll also say that it could be worth considering a shot at a software solution built for DIY landlords (1 - 15 units) to bring some automation to the rental management process (just to make things much much easier for you)!

Read for yourself: Real Estate Broker 'Real estate broker'', hereinafter referred to as broker, any person who for another person and for a fee, commission or other valuable consideration, or with the intention or in the expectation or upon the promise of receiving or collecting a fee, commission or other valuable consideration, does any of the following:Sells, exchanges, purchases, rents or leases, or negotiates, or offers, attempts or agrees to negotiate the sale, exchange, purchase, rental or leasing of any real estate, or lists or offers, attempts or agrees to list any real estate, or buys or offers to buy, sells or offers to sell or otherwise deals in options on real estate, or advertises or holds himself out as engaged in the business of selling, exchanging, purchasing, renting or leasing real estate, or assists or directs in the procuring of prospects or the negotiation or completion of any agreement or transaction which results or is intended to result in the sale, exchange, purchase, leasing or renting of any real estate.

Agarwal agreed to negotiateand negotiated a potential purchase of property, agreed to list and listed, agreed to offer and offered a property for sale,advertised and held himself out as engaged in the business of selling real estate, directed and assisted in the procuring ofprospects and in the negotiation of a transaction which was calculated to result in the sale of a property and intended orexpected to receive compensation or other valuable consideration for the above conduct, while not licensed under Chapter4735.ELYHUE E.