We have 83 rental units. Dad's dream was always to have his kids working for him. To keep a long story short he started buying some in 1983 - a six townhouse unit. Since he was working full time didn't need the money he used the profits and colateral from that property to buy 6 more, and so on. He worked full time during the week and worked on the properties on the weekend. My dad always was a workaholic. Now after all this time we usually buy a fixer-upper over the winter when people don't move much and there is little to do outside unless it snows. We do all the management and maintenance, rental collection, refurbish when they move, and general day to day stuff. Often means weekends and evenings.
We have a lot of successes, we have a lot of horror stories. It is one of those businesses where you really have to have the right mentality of "take the good with the bad and it will all come out in the end". As far as the time, that depends on your area and the timing. There are some deals, some not. Around here the economy never really tanked like some areas. Our unemployment stayed below the national level.
As Ehouse said holds true in PA. We must give a 10 day notice before we can go to the District Justice, then it is a long drawn out process, about 2 months.
At least in NY you personally cannot evict a tenant even with out a lease. First a 3day notice, (pay or quit, not served by you, does not force tenant out.). Then a court date for a hearing, where in both sides are presented. Then if (if mind you) the judge finds in your favor, a 30 day notice (again served by your agent, again does not force tenant out). Then, the sheriff can be contacted and (for a fee) will physically evict in 72 hours. Takes about 2 months. You will be obliged to keep all tenants possessions safe and whole until he retrieves them, if I remember, for another 30 days. That's pretty much as I remember it.
One thing with management companies, we acquired a few from people who had management companies doing all the work. They get their money first, you get anything left. We attempt to work with people, appliances we get the "scratch and dent" (10% off) from Lowes and Home Depot, we shop around. A property management company don't bother. If a tentant needs a stove, they buy a stove whatever the cost, your paying not them. Same way with evictions. Again we have success and failures but we attempt a verbal warning first, then a notice and try to work out a deal. Evictions not only cost the money in lost rent but time, paperwork, and typically if someone is getting evicted they most certainly don't leave the place in tip top shape. A property management company sticks to the law and if it isn't there by the due date they start the process. Whether we have to meet the tenant at the bank, work, etc it is still cheaper then an eviction.
It can be rewarding, it can be a nightmare. Because we do the work ourselves and can afford it, our rents are below average for the area. Our average tenant stays 15 years. One thing for sure, everyday is an adventure. Good luck.