Hello and welcome!
My mentor suggests that a PROPERLY executed yellow letter campaign (search the forums here) will yield an 11%-15% response rate IF the mailing list is targeted.
Out of those responses who were motivated enough to respond, about 1 in 25 will be a deal(high motivation, high equity). In addition to the 1 wholesale deal about 3-4 people would be interested in either seller financing or subject-to.
As for finding leads on a shoestring budget, there are MANY posts in the wholesale forums here on BP that give proven examples from veterans.
Some of the most popular are:
Bandit Signs - It will help if you know where your buyers want to buy and saturate those areas. They aren't super cheap, but they are very effective. If you want to stretch your marketing dollar you can put them up on Friday nights and take them down Sunday evenings and use them again.
Driving for dollars - drive around your target areas and look for vacant and rundown houses. Use the county online tax assessors database to find out who owns the house (mine doesn't show the tax mailing address...grrrrr) When you find the owner, send them a yellow letter (see above)
Online free marketing - Craigslist, backpage, and kajiji are the major players. Market a couple times per week on each of these sites. There's debate about the quality level of lead you might get here, but hey....it only takes 1 person if they are the right person.
that should be good to get you started. there are plenty of other marketing methods, most of which can be costly. You'll be able to find more ideas than you need here in this forum. The marketing page on REICLUB also has a ton of info.
good luck